Three Hundred Years of Gravitation

Preprint

Full-text available

May 2023

Szymon Łukaszyk

Maxwell’s Equations in vacuum provide the negative speed of light

-c

, which leads to the imaginary set of base Planck units. However, the second, negative fine-structure constant

\alpha_2^{-1} \approx -140.178

, present in Fresnel coefficients for the normal incidence of electromagnetic radiation on monolayer graphene, establishes the different negative speed of light in vacuum

c_n \approx -3.06 \times 10^8~\text{[m/s]}

, which introduces the imaginary set of base Planck units different in magnitude from the ones parametrized with c. It follows that electric charges are the same in real and imaginary dimensions. We model neutron stars and white dwarfs, emitting perfect black-body radiation, as objects having energy exceeding their mass-energy equivalence ratios. We define complex energies in terms of real and imaginary natural units. Their imaginary parts, inaccessible for direct observation, store the excess of these energies. It follows that black holes are fundamentally uncharged, charged micro neutron stars and white dwarfs with masses lower than

5.7275 \times 10^{-10}~[\text{kg}]

are inaccessible for direct observation, and the radii of white dwarfs' cores are limited to

R_{\text{WD}} < 3.3967~R_{\text{BH}}

, where

R_{\text{BH}}

is the Schwarzschild radius of a white dwarf mass. It is conjectured that the maximum atomic number Z=238. A black-body object is in the equilibrium of complex energies of masses, charges, and photons if its radius

R_\text{eq} \approx 1.3833~R_{\text{BH}}

, which is marginally greater than a locally negative energy density bound of

4/3~R_{\text{BH}}

. Complex Newton’s law of universal gravitation, based on complex energies, leads to the black-body object's surface gravity and the generalized Hawking radiation temperature, which includes its charge. The proposed model takes into account the value(s) of the fine-structure constant(s), which is/are otherwise neglected in general relativity, and explains the registered (GWOSC) high masses of neutron stars' mergers and the associated fast radio bursts (CHIME) without resorting to any hypothetical types of exotic stellar objects.

The Imaginary Universe

Preprint

Full-text available

Apr 2023

Szymon Łukaszyk

Imaginary dimensions in physics require an imaginary set of base Planck units and some negative parameter

c_n

corresponding to the speed of light in vacuum c. The second, negative fine-structure constant

\alpha_2^{-1} \approx -140.178

is present in Fresnel coefficients for the normal incidence of electromagnetic radiation on monolayer graphene, leading to these imaginary Planck units, and it establishes

c_n \approx -3.06 \times 10^8~\text{[m/s]}

. It follows that electric charges are the same in real and imaginary dimensions. We model neutron stars and white dwarfs, emitting perfect black-body radiation, as objects having energy exceeding their mass-energy equivalence ratios. We define complex energies in terms of real and imaginary Planck units. Their imaginary parts, inaccessible for direct observation, store the excess of these energies. It follows that black holes are fundamentally uncharged, charged micro neutron stars and white dwarfs with masses lower than

5.7275 \times 10^{-10}~[\text{kg}]

are inaccessible for direct observation, and the radii of white dwarfs' cores are limited to

R_{\text{WD}} < 6.7933~G M_{\text{WD}}/c^2

. It is conjectured that the maximum atomic number Z=238. A black-body object is in the equilibrium of complex energies of masses, charges, and photons if its radius

R_\text{eq} \approx 2.7665~G M_{\text{BBO}}/c^2

, which corrects the value of the photon sphere radius

R_{\text{ps}}=3G M/c^2

, by taking into account the value(s) of the fine-structure constant(s), which is otherwise neglected in general relativity. Complex Newton’s law of universal gravitation, based on complex energies, leads to the black-body object's surface gravity and the generalized Hawking radiation temperature, which includes its charge. The proposed model explains the registered (GWOSC) high masses of neutron stars' mergers without resorting to any hypothetical types of exotic stellar objects.

The Imaginary Universe

Preprint

Dec 2022

Szymon Łukaszyk

Maxwell’s equations in vacuum provide the negative speed of light −c, which leads to imaginary Planck units. However, the second, negative fine-structure constant α_2^−1 ≈ −140.178, present in the Fresnel coefficients for the normal incidence of electromagnetic radiation on monolayer graphene, establishes the different, negative speed of light in vacuum c_2 ≈ −3.06 × 10^8 [m/s], which introduces imaginary Planck units different in magnitude from those parametrized with c. Furthermore, algebraic relations between the fine-structure constants hint that the fine-structure constant does not vary over time. It follows that electric charges are the same in real and imaginary dimensions. We model neutron stars and white dwarfs, emitting perfect black-body radiation, as objects having energy exceeding their mass-energy equivalence ratios. We define complex energies in terms of real and imaginary natural units. Their imaginary parts, inaccessible for direct observation, store the excess of these energies. It is conjectured that the maximum atomic number Z = 238. A black-body object is in the equilibrium of complex energies if its radius R_eq ≈ 1.3833 R_BH, which is close to the photon sphere radius R_ps = 1.5 R_BH, and marginally greater than a locally negative energy density bound of 4/3 R_BH. The complex force between real masses and imaginary charges leads to the black-body object’s surface gravity and generalized Hawking radiation temperature, which includes its charge. Furthermore, this force agrees with the physical parameters of the hydrogen atom. The proposed model takes into account the value(s) of the fine-structure constant(s), which is/are otherwise neglected in general relativity, and explains the registered (GWOSC) high masses of neutron stars’ mergers and the associated fast radio bursts (CHIME) without resorting to any hypothetical types of exotic stellar objects.

Polarization states of gravitational waves detected by LIGO-Virgo antennas

Thesis

Full-text available

Jun 2017

Liudmila Fesik

The detection of the first gravitational wave events by the Advanced LIGO Scientific Collaboration has opened a new possibility for the study of fundamental physics of gravitational interaction. This work conducts an analysis of possible polarization states of gravitational waves (GW) radiated by the most promising types of sources to be detected by the modern interferometric antennas: coalescing compact binaries and collapsing supernovae. Several theoretical approaches to the current as well as future gravitational wave signals interpretation are discussed together with a strategy for a search for corresponding transients by means of multimessenger astronomy. One of the aims of this thesis is to develop a new method for GW source localization depending on a polarization state of an incoming GW in the case of a detection by two interferometric antennas. Additionally, there is elaborated a further method focused on a possibility to recognise different polarization states of a GW detected by means of a network with three and more antennas in operation. The both proposed methods have been applied to the LIGO events GW150914, GW151226 and LVT151012, together with the matching of the results with the currently known electromagnetic follow-ups to these GW events. The conclusion of this research is that there are opportunities for verifying different predictions of the scalar-tensor theories of gravitation by means of the analysis of the polarization states of the detected gravitational waves. All in all, this work provides a new test of the theoretical assumptions about the nature of gravity as well as about the processes in relativistic compact objects of various types.

A New Gravitational Wave Probe to the Nature of Dark Energy from the Aging of the Universe: Can Future Detectors Achieve it?

Preprint

Jun 2024

Suvodip Mukherjee

One of the most dominant energy budget of the Universe is Dark Energy, which remains enigmatic since the claim of its existence from the observation of late-time cosmic acceleration. We propose a new way of inferring this by measuring the aging of the Universe using only gravitational wave (GW) signals from coalescing binary compact objects of any masses. We show that the aging of the Universe will lead to a change in the observed chirp mass of the GW sources inferred from different stages of its coalesces by monitoring a coherent source from two far-apart GW frequencies for a few years. We show that coordinated GW detectors which can reach a relative uncertainty on chirp mass measurement of about

10^{-9}

, can measure a tiny departure of about

2\%

from the dark energy equation of state parameter

w_0=-1

and its variation with cosmic time by using stellar origin binary black holes up to redshift z=5 in 10 years of observation time without using any external calibrator. If the next generation of GW detectors can achieve this precision, then it can open a new window to discover the fundamental nature of dark energy.

A New Theory of Formation of Compact Stellar Objects

Preprint

Full-text available

Sep 2021

We propose a novel idea for the formation of compact stars. In an attempt of exploiting the elegance of Boltzmann's factor we propose the relations for density variation of the compact stars. Consequently, we found Chandrasekhar limit of white dwarf stars and Tolman-Oppenheimer-Volkoff limit for neutron stars. We further extended the theory to propose the corresponding limits for black holes and the big core that is formed out of the visible universe. The limit of the big core is √ 2 times the mass of the observable universe. This enables us to claim that the Chandrasekhar limit is the basic unit of all compact core limits. There can be a hierarchy of compact cores depending upon the binding energy of the body from which it is formed. Every uniform distribution leads to a compact core and every compact core becomes the base distribution for another compact core, and so on. The higher mass limit is connected to the immediate lower limit by a factor of √ 2. The theory has the potential to study any structure formation in the universe from two-particle correlations to galaxy clusters to compact objects and to the big bang of the universe. We applied the reverse of core formation to study the big bang expansion and the cooling of the universe. We found the theory agrees with the heat death of the universe.

A New Theory of Formation of Compact Stellar Objects

Preprint

Full-text available

Jan 2020

We propose a novel idea for the formation of compact stars. In an attempt of exploiting the elegance of Boltzmann's factor we propose the relations for density variation of the compact stars. Consequently, we found Chandrasekhar limit of white dwarf stars and Tolman-Oppenheimer-Volkoff limit for neutron stars. We further extended the theory to propose the corresponding limits for black holes and the big core that is formed out of the visible universe. The limit of the big core is √ 2 times the mass of the observable universe. This enables us to claim that the Chandrasekhar limit is the basic unit of all compact core limits. There can be a hierarchy of compact cores depending upon the binding energy of the body from which it is formed. Every uniform distribution leads to a compact core and every compact core becomes the base distribution for another compact core, and so on. The higher mass limit is connected to the immediate lower limit by a factor of √ 2. The theory has the potential to study any structure formation in the universe from two-particle correlations to galaxy clusters to compact objects and to the big bang of the universe. We applied the reverse of core formation to study the big bang expansion and the cooling of the universe. We found the theory agrees with the heat death of the universe.

Prospects of Detecting the Global HI-21cm Signal at uGMRT through the Gravitational Lensing by an isolated Neutron Star

Preprint

Full-text available

Jun 2024

The strength of the global HI-21cm signal is several orders of magnitude lower than the foreground and background noise and hence it is difficult to observe this signal at a given radio telescope. However, a few recent studies reported the detection of that signal at the radio band suggests the strength of this signal is somehow magnified. In this analysis, we study the prospects of detecting this global signal at different frequency bands of uGMRT where this global signal is supposed to be amplified through the strong gravitational lensing by an isolated neutron star located in a cosmological distance. Our study shows the effects of the lensing parameters on the observables of that amplified global signal and discusses its variation with the frequency bands considered here. We present a method to estimate the position and size of an isolated neutron star using the signal-to-noise ratio of that global signal supposed to be detected at different frequency bands of uGMRT. We discuss the scope of multi-messenger astronomy in the era of HI-21cm observation where the estimated lensing parameters can be cross-validated using the pulsar detection at the X-ray band from the same location in the sky. Our analysis is equally applicable to any radio telescope with given specifications.

The Imaginary Universe

Preprint

Full-text available

Aug 2023

Szymon Łukaszyk

Maxwell’s equations in vacuum provide the negative speed of light

-c

, which leads to imaginary Planck units. However, the second, negative fine-structure constant

\alpha_2^{-1} \approx -140.178

, present in the Fresnel coefficients for the normal incidence of electromagnetic radiation on monolayer graphene, establishes the different, negative speed of light in vacuum

c_2 \approx -3.06 \times 10^8~\text{[m/s]}

, which introduces imaginary Planck units different in magnitude from those parametrized with c. It follows that electric charges are the same in real and imaginary dimensions. We model neutron stars and white dwarfs, emitting perfect black-body radiation, as \textit{objects} having energy exceeding their mass-energy equivalence ratios. We define complex energies in terms of real and imaginary natural units. Their imaginary parts, inaccessible for direct observation, store the excess of these energies. It follows that black holes are fundamentally uncharged, masses of charged neutron stars and white dwarfs satisfy

M \lesssim 5.7275 \times 10^{-10}~[\text{kg}]

, and the radii of white dwarfs' cores are limited to

R_{\text{WD}} \lesssim 3.3967~R_{\text{BH}}

, where

R_{\text{BH}}

is the Schwarzschild radius of a white dwarf mass. It is conjectured that the maximum atomic number Z=238. A black-body \textit{object} is in the equilibrium of complex energies if its radius

R_\text{eq} \approx 1.3833~R_{\text{BH}}

, which is close to the photon sphere radius

R_{\text{ps}}=1.5~R_{\text{BH}}

, and marginally greater than a locally negative energy density bound of

4/3~R_{\text{BH}}

. Complex Newton’s law of universal gravitation, based on complex energies, leads to the black-body object's surface gravity and the generalized Hawking radiation temperature, which includes its charge. The proposed model takes into account the value(s) of the fine-structure constant(s), which is/are otherwise neglected in general relativity, and explains the registered (GWOSC) high masses of neutron stars' mergers and the associated fast radio bursts (CHIME) without resorting to any hypothetical types of exotic stellar \textit{objects}.

Probing

z \gtrsim 6

massive black holes with gravitational waves

Preprint

Full-text available

May 2023

We investigate the coalescence of massive black hole (

M_{\rm BH}\gtrsim 10^{6}~\rm M_{\odot}

) binaries (MBHBs) at

6<z<10

by adopting a suite of cosmological hydrodynamical simulations of galaxy formation, zoomed-in on biased (

>3 \sigma

) overdense regions (

M_h\sim 10^{12}~\rm M_{\odot}

dark matter halos at

z = 6

) of the Universe. We first analyse the impact of different resolutions and AGN feedback prescriptions on the merger rate, assuming instantaneous mergers. Then, we compute the halo bias correction factor due to the overdense simulated region. Our simulations predict merger rates that range between 3 - 15

\rm yr^{-1}

at

z\sim 6

, depending on the run considered, and after correcting for a bias factor of

\sim 20-30

. For our fiducial model, we further consider the effect of delay in the MBHB coalescence due to dynamical friction. We find that 83 per cent of MBHBs will merge within the Hubble time, and 21 per cent within 1 Gyr, namely the age of the Universe at

z > 6

. We finally compute the expected properties of the gravitational wave (GW) signals and find the fraction of LISA detectable events with high signal-to-noise ratio (SNR

>

5) to range between 66-69 per cent. However, identifying the electro-magnetic counterpart of these events remains challenging due to the poor LISA sky localization that, for the loudest signals (

\mathcal M_c\sim 10^6~\rm M_{\odot}

at z=6), is around 10

\rm deg^2

.

The Imaginary Universe

Preprint

Full-text available

May 2023

Szymon Łukaszyk

Maxwell’s Equations in vacuum provide the negative speed of light

-c

, which leads to the imaginary set of base Planck units. However, the second, negative fine-structure constant

\alpha_2^{-1} \approx -140.178

, present in Fresnel coefficients for the normal incidence of electromagnetic radiation on monolayer graphene, establishes the different negative speed of light in vacuum

c_n \approx -3.06 \times 10^8~\text{[m/s]}

, which introduces the imaginary set of base Planck units different in magnitude from the ones parametrized with c. It follows that electric charges are the same in real and imaginary dimensions. We model neutron stars and white dwarfs, emitting perfect black-body radiation, as objects having energy exceeding their mass-energy equivalence ratios. We define complex energies in terms of real and imaginary natural units. Their imaginary parts, inaccessible for direct observation, store the excess of these energies. It follows that black holes are fundamentally uncharged, charged micro neutron stars and white dwarfs with masses lower than

5.7275 \times 10^{-10}~[\text{kg}]

are inaccessible for direct observation, and the radii of white dwarfs' cores are limited to

R_{\text{WD}} < 3.3967~R_{\text{BH}}

, where

R_{\text{BH}}

is the Schwarzschild radius of a white dwarf mass. It is conjectured that the maximum atomic number Z=238. A black-body object is in the equilibrium of complex energies of masses, charges, and photons if its radius

R_\text{eq} \approx 1.3833~R_{\text{BH}}

, which is marginally greater than a locally negative energy density bound of

4/3~R_{\text{BH}}

. Complex Newton’s law of universal gravitation, based on complex energies, leads to the black-body object's surface gravity and the generalized Hawking radiation temperature, which includes its charge. The proposed model takes into account the value(s) of the fine-structure constant(s), which is/are otherwise neglected in general relativity, and explains the registered (GWOSC) high masses of neutron stars' mergers and the associated fast radio bursts (CHIME) without resorting to any hypothetical types of exotic stellar objects.

The Imaginary Universe

Preprint

Full-text available

Apr 2023

Szymon Łukaszyk

Imaginary dimensions in physics require an imaginary set of base Planck units and some negative parameter

c_n

corresponding to the speed of light in vacuum c. The second, negative fine-structure constant

\alpha_2^{-1} \approx -140.178

is present in Fresnel coefficients for the normal incidence of electromagnetic radiation on monolayer graphene, leading to these imaginary Planck units, and it establishes

c_n \approx -3.06 \times 10^8~\text{[m/s]}

. It follows that electric charges are the same in real and imaginary dimensions. We model neutron stars and white dwarfs, emitting perfect black-body radiation, as objects having energy exceeding their mass-energy equivalence ratios. We define complex energies in terms of real and imaginary Planck units. Their imaginary parts, inaccessible for direct observation, store the excess of these energies. It follows that black holes are fundamentally uncharged, charged micro neutron stars and white dwarfs with masses lower than

5.7275 \times 10^{-10}~[\text{kg}]

are inaccessible for direct observation, and the radii of white dwarfs' cores are limited to

R_{\text{WD}} < 6.7933~G M_{\text{WD}}/c^2

. It is conjectured that the maximum atomic number Z=238. A black-body object is in the equilibrium of complex energies of masses, charges, and photons if its radius

R_\text{eq} \approx 2.7665~G M_{\text{BBO}}/c^2

, which corrects the value of the photon sphere radius

R_{\text{ps}}=3G M/c^2

, by taking into account the value(s) of the fine-structure constant(s), which is otherwise neglected in general relativity. Complex Newton’s law of universal gravitation, based on complex energies, leads to the black-body object's surface gravity and the generalized Hawking radiation temperature, which includes its charge. The proposed model explains the registered (GWOSC) high masses of neutron stars' mergers and the associated fast radio bursts (CHIME) without resorting to any hypothetical types of exotic stellar objects.

Data Analysis for Gravitational Waves Using Neural Networks on Quantum Computers

Article

Full-text available

Aug 2022

In this study, we evaluate the feasibility of using quantum neural networks for classifying gravitational waveforms, using both simulators and quantum computers. The analysis is quite interdisciplinary in its nature, combining knowledge involving astrophysics, quantum information as well as quantum and classical machine learning. We showed that the quantum classifiers and hybrid classical-quantum layers give highly accurate results when tested on a simple dataset and ran on a simulator; also, adding a quantum layer to poorly performing classical neural network can highly improve its accuracy. When running on a real quantum computer, error minimizing algorithms need to be implemented in order to obtain a satisfying accuracy.

Global well-posedness for a class of semilinear hyperbolic equations with singular potentials on manifolds with conical singularities

Article

Full-text available

Sep 2022
CALC VAR PARTIAL DIF

This paper is concerned with a class of semilinear hyperbolic equations with singular potentials on the manifolds with conical singularities, which was introduced to describe a field propagating on the spacetime of a true string. We prove the local existence and uniqueness of the solution by using the contraction mapping principle. In the spirit of variational principle and mountain pass theorem, a class of initial data are precisely divided into three different energy levels. The main ingredient of this paper is to conduct a comprehensive and systematic study on the dynamic behavior of the solution with three different energy levels. We introduce a family of potential wells to derive a threshold of the existence of global solutions and blow up in finite time of solution in both cases with sub-critical and critical initial energy. Moreover, two sets of sufficient conditions for initial data leading to blow up result are established at arbitrarily positive initial energy level.

Boosting the Efficiency of Parametric Detection with Hierarchical Neural Networks

Preprint

Jul 2022

Gravitational wave astronomy is a vibrant field that leverages both classic and modern data processing techniques for the understanding of the universe. Various approaches have been proposed for improving the efficiency of the detection scheme, with hierarchical matched filtering being an important strategy. Meanwhile, deep learning methods have recently demonstrated both consistency with matched filtering methods and remarkable statistical performance. In this work, we propose Hierarchical Detection Network (HDN), a novel approach to efficient detection that combines ideas from hierarchical matching and deep learning. The network is trained using a novel loss function, which encodes simultaneously the goals of statistical accuracy and efficiency. We discuss the source of complexity reduction of the proposed model, and describe a general recipe for initialization with each layer specializing in different regions. We demonstrate the performance of HDN with experiments using open LIGO data and synthetic injections, and observe with two-layer models a

79\%

efficiency gain compared with matched filtering at an equal error rate of

0.2\%

. Furthermore, we show how training a three-layer HDN initialized using two-layer model can further boost both accuracy and efficiency, highlighting the power of multiple simple layers in efficient detection.

Magnetized relativistic accretion disk around a spinning, electrically charged, accelerating black hole: Case of the C metric

Article

Full-text available

May 2022

This paper examines the general relativistic model of a geometrically thick configuration of an accretion disk around an electrically charged black hole in an accelerated motion, as described by the C-metric family. We aim to study effects of the spacetime background on the magnetized version of the thick disk model via the sequences of figures of equilibrium. While maintaining the assumption of non-self-gravitating (test) fluid, we newly explore the influence of the strength of the large-scale magnetic field with field lines organised over the length scale of the black-hole horizon. We systematically analyze the dependence on a very broad parameter space of the adopted scenario. We demonstrate that the C metric can, in principle, be distinguished from Kerr black-hole metric by resolving specific (albeit rather fine) features of the torus, such as the location of its center, inner, and outer rims, and the overall shape. The analytical setup can serve as a test bed for numerical simulations.

Impact of astrophysical binary coalescence timescales on the rate of lensed gravitational wave events

Preprint

Full-text available

Jun 2021

The expected event rate of lensed gravitational wave sources scales with the merger rate at redshift

z\geq 1

, where the optical depth for lensing is high. It is commonly assumed that the merger rate of the astrophysical compact objects is closely connected with the star formation rate, which peaks around redshift

z\sim 2

. However, a major source of uncertainty is the delay time between the formation and merger of compact objects. We explore the impact of delay time on the lensing event rate. We show that as the delay time increases, the peak of the merger rate of gravitational wave sources gets deferred to a lower redshift. This leads to a reduction in the event rate of the lensed events which are detectable by the gravitational wave detectors. We show that for a delay time of around 10 Gyr or larger, the lensed event rate can be less than one per year for the design sensitivity of LIGO/Virgo. We also estimate the merger rate for lensed sub-threshold for different delay time scenarios, finding that for larger delay times the number of lensed sub-threshold events is reduced, whereas for small-delay time models they are significantly more frequent. This analysis shows for the first time that lensing is a complementary probe to explore different formation channels of binary systems by exploiting the lensing event rate from the well-detected events and sub-threshold events which are measurable using the network of gravitational wave detectors.

Testing the general theory of relativity using gravitational wave propagation from dark standard sirens

Article

Full-text available

Jan 2021
MON NOT R ASTRON SOC

Alternative theories of gravity predict modifications in the propagation of gravitational waves (GW) through space-time. One of the smoking-gun predictions of such theories is the change in the GW luminosity distance to GW sources as a function of redshift relative to the electromagnetic (EM) luminosity distance expected from EM probes. We propose a multi-messenger test of the theory of general relativity from the propagation of gravitational waves by combining EM and GW observations to resolve these issues from GW sources without EM counterparts (which are also referred to as dark standard sirens). By using the relation between the geometric distances accessible from baryon acoustic oscillation measurements, and luminosity distance measurements from the GW sources, we can measure any deviation from the general theory of relativity via the GW sources of unknown redshift that will be detectable by networks of GW detectors such as LIGO, Virgo, and KAGRA. Using this technique, the fiducial value of the frictional term can be measured to a precision

\Xi _0=0.98^{+0.04}_{-0.23}

after marginalizing over redshift dependence, cosmological parameters, and GW bias parameters with ∼3500 dark standard sirens of masses

30\, \rm M_\odot

each distributed up to redshift z = 0.5. For a fixed redshift dependence, a value of

\Xi _0=0.99^{+0.02}_{-0.02}

can be measured with a similar number of dark sirens. Application of our methodology to the far more numerous dark standard sirens detectable with next generation GW detectors, such as LISA, Einstein Telescope and Cosmic Explorer, will allow achievement of higher accuracy than possible from use of bright standard sirens.

Quantum black hole spectroscopy: probing the quantum nature of the black hole area using LIGO-Virgo ringdown detections

Preprint

Nov 2020

We present a thorough observational investigation of the heuristic quantised ringdown model presented in Foit & Kleban (2019). This model is based on the Bekenstein-Mukhanov conjecture, stating that the area of a black hole horizon is an integer multiple of the Planck area

l_P^2

multiplied by a phenomenological constant,

\alpha

, which can be viewed as an additional black hole intrinsic parameter. Our approach is based on a time-domain analysis of the gravitational wave signals produced by the ringdown phase of binary black hole mergers detected by the LIGO and Virgo collaboration. Employing a full Bayesian formalism and taking into account the complete correlation structure among the black hole parameters, we show that the value of

\alpha

cannot be constrained using only GW150914, in contrast to what was suggested in Foit & Kleban (2019). We proceed to repeat the same analysis on the new gravitational wave events detected by the LIGO and Virgo Collaboration up to 1 October 2019, obtaining a combined-event measure equal to

\alpha = 15.6^{+20.5}_{-13.3}

and a combined log odds ratio of

0.1 \pm 0.6

, implying that current data are not informative enough to favour or discard this model against general relativity. We then show that using a population of

\mathcal{O}(20)

GW150914-like simulated events - detected by the current infrastructure of ground-based detectors at their design sensitivity - it is possible to confidently falsify the quantised model or prove its validity, in which case probing

\alpha

at the few % level. Finally we classify the stealth biases that may show up in a population study.

Probing the theory of gravity with gravitational lensing of gravitational waves and galaxy surveys

Article

May 2020
MON NOT R ASTRON SOC

The cross-correlation of gravitational wave strain with upcoming galaxy surveys probes theories of gravity in a new way. This method enables testing the theory of gravity by combining the effects from both gravitational lensing of gravitational waves and the propagation of gravitational waves in space–time. We find that within 10 yr the combination of the Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory) and VIRGO (Virgo interferometer) detector networks with planned galaxy surveys should detect weak gravitational lensing of gravitational waves in the low-redshift Universe (z < 0.5). With the next-generation gravitational wave experiments such as Voyager, LISA (Laser Interferometer Space Antenna), Cosmic Explorer, and the Einstein Telescope, we can extend this test of the theory of gravity to larger redshifts by exploiting the synergies between electromagnetic wave and gravitational wave probes.

SOME BIANCHI TYPE BULK VISCOUS STRING COSMOLOGICAL MODELS IN f (R) GRAVITY

Article

Full-text available

Oct 2019

In this paper, we investigate bianchi type II, V III and IX Bulk viscous string cosmological models in the context of f (R) gravity. Here, we obtained the solutions of the field equations in the presence of cosmic strings under some specific possible physical conditions. Some physical and geometrical features of the models are also discussed.

Some Bianchi Type Bulk Viscous String Cosmological Models in f ( R ) Gravity

Article

Full-text available

Oct 2019

In this paper, we investigate bianchi type II, V III and IX Bulk viscous string cosmological models in the context of f ( R ) gravity. Here, we obtained the solutions of the field equations in the presence of cosmic strings under some specific possible physical conditions. Some physical and geometrical features of the models are also discussed.

Velocity debiasing for Hubble constant measurements from standard sirens

Preprint

Full-text available

Sep 2019

Gravitational wave (GW) sources are an excellent probe of the luminosity distance and offer a novel measure of the Hubble constant,

H_0

. This estimation of

H_0

from standard sirens requires an accurate estimation of the cosmological redshift of the host galaxy of the GW source, after correcting for its peculiar velocity. Absence of an accurate peculiar velocity correction affects both the precision and accuracy of the measurement of

H_0

, particularly for nearby sources. We propose a framework to incorporate such a peculiar velocity correction for GW sources. The implementation of our method to the event GW170817 combined with the Very Large Baseline Interferometry (VLBI) observation leads to a revised value of

H_0= 69.3^{+ 4.5}_{-4.0}

km s

^{-1}

Mpc

^{-1}

; more importantly, it demonstrates that our method will allow to achieve in practice unbiased, accurate measurements of

H_0

at the precision promised by standard siren forecasts.

Probing the theory of gravity with gravitational lensing of gravitational waves and galaxy surveys

Preprint

Full-text available

Aug 2019

The cross-correlation of gravitational wave events with upcoming galaxy surveys probe theories of gravity in a fundamentally new way, with the potential to reveal clues as to the nature of dark energy and dark matter. We find that within 10 years, the combination of the Advanced-LIGO and VIRGO detector network with planned galaxy surveys can detect weak gravitational lensing of gravitational waves in the low redshift Universe (

z<0.5

). With the next generation gravitational wave experiments such as Voyager, LISA, Cosmic-Explorer and Einstein Telescope, we can extend the range of this probe up to a redshift of

z\sim 20

. This new probe will test the theory of gravity using both gravitational wave propagation through spacetime and also the effect of cosmic structures on gravitational waves, opening up a new observational window for cosmology and fundamental physics.

Any extremal black holes are primordial

Preprint

Jun 2019

Extremal Kerr black holes, if they exist, cannot have an astrophysical origin due to the Thorne limit

a<a^*_{\rm lim}=0.998

. However this limit can be evaded if they are primordial and subject to evaporation by Hawking radiation. We derive the lower mass limit above which Hawking radiation is slow enough so that a primordial black hole with a spin initially above the Thorne limit can still be above this limit today. Thus, the observation of a Kerr black hole with

a^* > a^*_{\rm lim}

should be a proof of its primordial origin.

Intensification of Gravitational Wave Field Near Compact Star

Preprint

Full-text available

Feb 2019

The gravitational waves (GWs) has been a topic of interest for its versatile capabilities of probing several aspects of cosmology and early Universe. Gravitational lensing enhances further the extent of this sort of waves and upgrade our understanding to a next level. Besides several similarities with optical waves, GWs are capable of passing through optically opaque celestial objects like stars, exoplanets unlike light waves and manifest a different kind of lensing effect. In this work we have explored the lensing action of compact objects on gravitational waves using numerical means. After modeling the internal mass distribution of the compact objects by TOV equations and tracing wavefronts using geodesic equations, we have found that the GWs are indeed lensed in a manner analogous to the optical lensing of light in presence of a thick optical lens by producing spherical aberration in the focused waves. The distance to the best focused point shows significant dependence with the mass and radius of the lensing star and unlike gravitational lensing, the region inside and outside compact objects responds differently to the incoming waves.

Numerical conservation of exact and approximate first post-Newtonian energy integrals

Conference Paper

Sep 2018

The incorporation of Albert Einstein's theory of gravitation is necessary for any satellite mission requiring highly precise orbit information. For near-Earth objects, this is achieved using the first post-Newtonian approximation. In this article, we derive an exact analytical expression for the energy of a test particle in the spherically symmetric Schwarzschild field of the Earth by seeking a Jacobi-like integral associated with the post-Newtonian equations of motion. The energy integral so obtained contains exponential terms which when approximated produce results which are well established in the literature. Using structure-preserving symplectic numerical integration schemes, we demonstrate that the integral containing exponential terms more accurately describes the true conserved dynamics of test particles in the PN regime as compared with the existing approximations of the energy invariants.

The Emergence of Gravitational Wave Science: 100 Years of Development of Mathematical Theory, Detectors, Numerical Algorithms, and Data Analysis Tools

Article

Jul 2016

On September 14, 2015, the newly upgraded Laser Interferometer Gravitational-wave Observatory (LIGO) recorded a loud gravitational-wave (GW) signal, emitted a billion light-years away by a coalescing binary of two stellar-mass black holes. The detection was announced in February 2016, in time for the hundredth anniversary of Einstein's prediction of GWs within the theory of general relativity (GR). The signal represents the first direct detection of GWs, the first observation of a black-hole binary, and the first test of GR in its strong-field, high-velocity, nonlinear regime. In the remainder of its first observing run, LIGO observed two more signals from black-hole binaries, one moderately loud, another at the boundary of statistical significance. The detections mark the end of a decades-long quest, and the beginning of GW astronomy: finally, we are able to probe the unseen, electromagnetically dark Universe by listening to it. In this article, we present a short historical overview of GW science: this young discipline combines GR, arguably the crowning achievement of classical physics, with record-setting, ultra-low-noise laser interferometry, and with some of the most powerful developments in the theory of differential geometry, partial differential equations, high-performance computation, numerical analysis, signal processing, statistical inference, and data science. Our emphasis is on the synergy between these disciplines, and how mathematics, broadly understood, has historically played, and continues to play, a crucial role in the development of GW science. We focus on black holes, which are very pure mathematical solutions of Einstein's gravitational-field equations that are nevertheless realized in Nature, and that provided the first observed signals.

Exploring gravity

Thesis

Jan 2014

C. P. L. Berry

Gravitation is the dominant influence in most astrophysical interactions. Weak-field interactions have been extensively studied, but the strong-field regime remains largely unexplored. Gravitational waves (GWs) are an excellent means of accessing strong-field regions. We investigate what we can learn about both astrophysics and gravitation from strong-field tests and, in particular, GWs; we focus upon extreme-mass-ratio (EMR) systems where a small body orbits a much more massive one. EMR bursts, a particular class of GW signals, could be used to determine the properties of massive black holes (MBHs). They could be detectable with a space-borne interferometer from many nearby galaxies, as well as the Galactic centre. Bursts could provide insightful constraints on the MBHs' parameters. These could elucidate the formation history of the MBHs and, by association, their host galaxies. The Galactic centre is the most promising source. Its event rate is determined by the stellar distribution surrounding the MBH; the rate is not high, but we still expect to gain useful astronomical information from bursts. Strong-field tests may reveal deviations from general relativity (GR). We calculate modifications that could be observed assuming metric f(R)-gravity as an effective alternative theory. Gravitational radiation is modified, as are planetary precession rates. Both give a means of testing GR. However, existing laboratory measurements already place tighter constraints on f(R)-gravity, unless there exists a screening effect, such as the chameleon mechanism, which suppresses modifications on small scales. To make precision measurements of astrophysical systems or place exacting bounds on deviations from GR, we must have accurate GW templates. Transient resonances are currently not included in the prescription for generating EMR inspiral waveforms. Their effects can be estimated from asymptotic expansions of the evolving orbital parameters. The quantitative impact on parameter estimation has yet to be calculated, but it appears that it shall be necessary to incorporate resonances when creating inspiral waveforms.

Gravitational wave astronomy: the current status

Article

Full-text available

Feb 2016

In the centenary year of Einstein's General Theory of Relativity, this paper reviews the current status of gravitational wave astronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Sect. 1 of this paper reviews the historical development of gravitational wave astronomy from Einstein's first prediction to our current understanding the spectrum. It is shown that detection of signals in the audio frequency spectrum can be expected very soon, and that a north-south pair of next generation detectors would provide large scientific benefits. Sect. 2 reviews the theory of gravitational waves and the principles of detection using laser interferometry. The state of the art Advanced LIGO detectors are then described. These detectors have a high chance of detecting the first events in the near future. Sect. 3 reviews the KAGRA detector currently under development in Japan, which will be the first laser interferometer detector to use cryogenic test masses. Sect. 4 of this paper reviews gravitational wave detection in the nanohertz frequency band using the technique of pulsar timing. Sect. 5 reviews the status of gravitational wave detection in the attohertz frequency band, detectable in the polarisation of the cosmic microwave background, and discusses the prospects for detection of primordial waves from the big bang. The techniques described in sects. 1-5 have already placed significant limits on the strength of gravitational wave sources. Sects. 6 and 7 review ambitious plans for future space based gravitational wave detectors in the millihertz frequency band. Sect. 6 presents a roadmap for development of space based gravitational wave detectors by China while sect. 7 discusses a key enabling technology for space interferometry known as time delay interferometry.

Gravitation, Ozone Layer And Others Information In Surah Ar-Rahman

Article

Nov 2024

Syed Abrar Tasnim

The word ‘nazm’which is mentioned in surah Ar Rahman at verse 06 is mass controversial, that, is it stars or grassiness ? And various interpreters have interpreted the word ‘mizan’ in various ways which is mentioned at verse 55:07 as scales, gold scales, scales of righteousness, scales of standard, justice and balance etc. And if it is discussed about general measurement at verse 55:09, then this would be clear irrelevant discussion of living world after that verses. I have presented my long days deep thinking, logic and strengthful document with proof to solve the complexity of verses. Revealed here in this study that the verses 05-12 in surah Rahman discussing gravitation and ozone layer, the most two significant subjects of physics but not about scales related to measurement .

On Covariant and Canonical Hamiltonian Formalisms for Gauge Theories

Article

Full-text available

Jan 2024

The Hamiltonian description of classical gauge theories is a very well studied subject. The two best known approaches, namely the covariant and canonical Hamiltonian formalisms, have received a lot of attention in the literature. However, a full understanding of the relation between them is not available, especially when the gauge theories are defined over regions with boundaries. Here, we consider this issue, by first making it precise what we mean by equivalence between the two formalisms. Then, we explore several first-order gauge theories and assess whether their corresponding descriptions satisfy the notion of equivalence. We shall show that, even when in several cases the two formalisms are indeed equivalent, there are counterexamples that signal that this is not always the case. Thus, non-equivalence is a generic feature of gauge field theories. These results call for a deeper understanding of the subject.

Method for In-orbit Redesign for TianQin Orbit Configuration

Article

Apr 2023
ADV SPACE RES

The space-based gravitational wave observatory mission consists of three drag-free controlled spacecraft, which form an equilateral triangle configuration. Due to the injection error, the configuration will deviate from the originally designed one, and the injection configuration cannot keep stability for a long term, which will affect the performance of the gravitational wave detection. In this study, we propose a method for reconfiguration using multiple-revolution Lambert solutions. In addition, assuming that the real-time data of spacecraft’s motion states can be obtained with high accuracy and the propulsion system can ensure the magnitude and accuracy of maneuvers, and taking the cost of reconfiguration and configuration stability requirements into account, a novel method of redesigning configuration based on differential evolution algorithm is proposed. Finally, the numerical simulations show that the redesigned configuration not only can reduce the maneuver cost significantly, but also can meet the requirements of long-term stability requirements.

Epistemology of Experimental Gravity - Scientific Rationality

Book

Full-text available

Nov 2019

Nicolae Sfetcu

The evolution of gravitational tests from an epistemological perspective framed in the concept of rational reconstruction of Imre Lakatos, based on his methodology of research programmes. Unlike other works on the same subject, the evaluated period is very extensive, starting with Newton's natural philosophy and up to the quantum gravity theories of today. In order to explain in a more rational way the complex evolution of the gravity concept of the last century, I propose a natural extension of the methodology of the research programmes of Lakatos that I then use during the paper. I believe that this approach offers a new perspective on how evolved over time the concept of gravity and the methods of testing each theory of gravity, through observations and experiments. I argue, based on the methodology of the research programmes and the studies of scientists and philosophers, that the current theories of quantum gravity are degenerative, due to the lack of experimental evidence over a long period of time and of self-immunization against the possibility of falsification. Moreover, a methodological current is being developed that assigns a secondary, unimportant role to verification through observations and/or experiments. For this reason, it will not be possible to have a complete theory of quantum gravity in its current form, which to include to the limit the general relativity, since physical theories have always been adjusted, during their evolution, based on observational or experimental tests, and verified by the predictions made. Also, contrary to a widespread opinion and current active programs regarding the unification of all the fundamental forces of physics in a single final theory, based on string theory, I argue that this unification is generally unlikely, and it is not possible anyway for a unification to be developed based on current theories of quantum gravity, including string theory. In addition, I support the views of some scientists and philosophers that currently too much resources are being consumed on the idea of developing quantum gravity theories, and in particular string theory, to include general relativity and to unify gravity with other forces, as long as science does not impose such research programs.

Might the 2PN Perihelion Precession of Mercury Become Measurable in the Next Future?

Article

Full-text available

Jan 2023

Lorenzo Iorio

The Hermean average perihelion rate ω˙2PN, calculated to the second post-Newtonian (2PN) order with the Gauss perturbing equations and the osculating Keplerian orbital elements, ranges from −18 to −4 microarcseconds per century μascty−1, depending on the true anomaly at epoch f0. It is the sum of four contributions: one of them is the direct consequence of the 2PN acceleration entering the equations of motion, while the other three are indirect effects of the 1PN component of the Sun’s gravitational field. An evaluation of the merely formal uncertainty of the experimental Mercury’s perihelion rate ω˙exp recently published by the present author, based on 51 years of radiotechnical data processed with the EPM2017 planetary ephemerides by the astronomers E.V. Pitjeva and N.P. Pitjev, is σω˙exp≃8μascty−1, corresponding to a relative accuracy of 2×10−7 for the combination 2+2γ−β/3 of the PPN parameters β and γ scaling the well known 1PN perihelion precession. In fact, the realistic uncertainty may be up to ≃10–50 times larger, despite reprocessing the now available raw data of the former MESSENGER mission with a recently improved solar corona model should ameliorate our knowledge of the Hermean orbit. The BepiColombo spacecraft, currently en route to Mercury, might reach a ≃10−7 accuracy level in constraining β and γ in an extended mission, despite ≃10−6 seems more likely according to most of the simulations currently available in the literature. Thus, it might be that in the not-too-distant future, it will be necessary to include the 2PN acceleration in the Solar System’s dynamics as well.

Pipeline for Detection of Transient Objects in Optical Surveys

Chapter

Jan 2022

Identification and following study of optical transients (OTs) associated with cosmic gamma-ray bursts (GRBs) and gravitational wave (GWs) events is a relevant research problem of multi-messenger astronomy. Since their first discovery, one of the greatest challenges is the localisation uncertainty. The sources of OTs are initially localised with space gamma and X-ray telescopes or ground-based laser interferometers LIGO, Virgo and KAGRA having the poor positional accuracy on average. A joint localisation area typically covers about 1000 deg

^{2}

of the sky based on previous runs of LIGO and Virgo. The last 25 years has seen a rapid development of the robotic optical surveys. Such instruments equipped with wide-field cameras allow to cover the entire localisation area in several scans. As the result, a massive amount of scientific products is generated, including bulky series of astronomical images. After their processing, large object catalogues that may contain up to

10^5

celestial objects are created. It is necessary to identify the peculiar objects among other in the formed catalogues. Both data processing and identification of OTs must be carried out in real-time due to steep decay of brightness. To response pointed problems, the software pipelines are becoming a relevant solution. This paper provides a complete overview of the units of the actively developed pipeline for OT detection. The accuracy and performance metrics of the pipeline units, estimated for two wide-field telescopes are given. In conclusions, the future plans for the development are briefly discussed.KeywordsOptical transientsLIGOVirgoKAGRAKilonovaeGamma-ray burstsReal-time image processing

General Relativistic and Post-Newtonian Dynamics for Near-Earth Objects and Solar System Bodies

Book

Full-text available

Oct 2021

Joseph O'Leary

Owing to the increased accuracy requirements in fields such as astrometry and geodesy the general theory of relativity must be taken into account for any mission requiring highly accurate orbit information and for practically all observation and measurement techniques. This book highlights the confluence of Applied Mathematics, Physics and Space Science as seen from Einstein's general theory of relativity and aims to bridge the gap between theoretical and applied domains. The book investigates three distinct areas of general relativity: Exact solutions of the Einstein field equations of gravitation. Dynamics of near-Earth objects and solar system bodies. Relativistic orbitography. This book is an updated and expanded version of the author’s PhD thesis which was awarded the International Astronomical Union PhD prize in Division A: Fundamental Astronomy. Included is a new introduction aimed at graduate students of General Relativity and extended discussions and results on topics in post-Newtonian dynamics and general relativistic spacecraft propagation.

Anomalies de la relativité générale

Preprint

Full-text available

Mar 2020

Nicolae Sfetcu

Au fil du temps, la théorie de la relativité générale a accumulé plusieurs anomalies, indiquant la nécessité de meilleures théories sur la gravité ou d'autres approches. Les hypothèses ad hoc introduites en relativité générale pour expliquer les singularités gravitationnelles basées sur les conditions énergétiques ne sont pas très efficaces. Des hypothèses plus détaillées sur le contenu du sujet sont nécessaires . De nombreux scientifiques et philosophes sont parvenus à la conclusion que les singularités doivent être associées à l'atteinte des limites de la validité physique de la relativité générale et qu'une nouvelle théorie, la gravité quantique, doit être développée.

Is the Copenhagen Interpretation Inapplicable to Quantum Cosmology?

Article

Full-text available

Aug 2020

Tatyana Shestakova

It is generally accepted that the Copenhagen interpretation is inapplicable to quantum cosmology, by contrast with the many worlds interpretation. I shall demonstrate that the two basic principles of the Copenhagen interpretation, the principle of wholeness and the principle of complementarity, do make sense in quantum gravity, since we can judge about quantum gravitational processes in the very early Universe by their vestiges in our macroscopic Universe. I shall present the extended phase space approach to quantum gravity and show that it can be interpreted in the spirit of the Everett’s “relative states” formulation, while there is no contradiction between the “relative states” formulation and the mentioned basic principles of the Copenhagen interpretation.

Stretching of the Super-Elastic Double-Helix Geon. Wheeler´s Thermal Geons as Quanta of Heat and Momentum. Bohm´s Diffusion and the Heating of the Solar Corona and Heating of the Earth - Geon Engineering. Milgrom-Verlinde Constant. Mareš - Šesták constant

Article

Full-text available

Mar 2020

Jiří Stávek

In our approach we have combined knowledge of Old Masters (working in this field before the year 1905), New Masters (working in this field after the year 1905) and Dissidents under the guidance of Louis de Broglie and David Bohm. Based on the great works of Julian Schwinger and John Archibald Wheeler we will study properties of geons formed by fusion of two soft x-ray particles (dyons) in the Schwarzschild gravitation core in our Sun at temperature 16 * 106 K. There are now several Teams that are able to achieve this fusion temperature in their special instruments (Tokamak, HL-2M Tokamak, Wendelstein 7-X, NIF, etc.) and to study properties of those formed geons. Thermal geons are with us all the time but they are very deeply hidden in our experiments. We have newly introduced Mareš - Šesták constant as the ratio of geon momentum to heat quantum of geon. The key information to enter into the World of geons was the empirical formula of David Bohm - the very well-known Bohm diffusion. From this formula we have extracted the amplitude, wavelength, frequency, quantum of the geon action, displacement law for geons, etc. It was found that geons are highly sensitive to the magnetic field strength. At a low magnetic field strength, the “inflation of geons” can occur. This effect could explain the Superheating of the Solar corona and the observed Heating of the Earth during two last centuries influenced by the changes in the Earth´s magnetic field. Geon engineering might modify the geon volume through the magnetic field strength. On the other hand, we were stimulated by the works of Mordehai Milgrom and Eric Verlinde and derived the Milgrom-Verlinde constant describing the gravitational field strength leading to the Newtonian gravitational constant on thermodynamic principles. The quantum of the geon momentum might open a new way how to understand gravitational phenomena. Can it be that Nature cleverly inserted geons into our experimental apparatuses and into our very-well known Old Formulae? We want to pass this concept into the hands of Readers of this Journal better educated in the Mathematics, Physics, and Thermodynamics.

Anomalies of General Relativity

Preprint

Full-text available

Oct 2019

Nicolae Sfetcu

Over time, the general theory of relativity has accumulated several anomalies and discrepancies, indicating the need for a better theory about gravity or other approaches. The ad-hoc hypotheses introduced in general relativity to explain gravitational singularities based on energy conditions are not very efficient. More detailed assumptions on the content of the subject are needed. Many scientists and philosophers have come to the conclusion that singularities must be associated with reaching the limits of the physical validity of general relativity, and a new theory of quantum gravity needs to be developed.

Epistémologie de la gravité expérimentale - Rationalité scientifique

Preprint

Full-text available

Mar 2020

Nicolae Sfetcu

L'évolution des tests gravitationnels dans une perspective épistémologique encadré dans le concept de reconstruction rationnelle d'Imre Lakatos, fondée sur sa méthodologie de programmes de recherche. Contrairement à d'autres travaux sur le même sujet, la période évaluée est très longue, allant de la philosophie naturelle de Newton aux théories de la gravité quantique d'aujourd'hui. Afin d'expliquer de manière plus rationnelle l'évolution complexe du concept de gravité du siècle dernier, je propose une extension naturelle de la méthodologie des programmes de recherche que j'utilisais ensuite au cours de la communication. Je pense que cette approche offre une nouvelle perspective sur la manière dont le concept de gravité et les méthodes de test de chaque théorie de la gravité ont évalué dans le temps, par le biais d'observations et d'expériences. Je soutiens, sur la base de la méthodologie des programmes de recherche et des études des scientifiques et des philosophes, que les théories actuelles de la gravité quantique sont dégénératives, en raison du manque de preuves expérimentales sur une longue période et d'auto-immunisation contre la possibilité de la réfutabilité. De plus, un courant méthodologique est en cours de développement, attribuant un rôle secondaire, sans importance, aux vérifications par le biais d'observations et / ou d'expériences. Pour cette raison, il ne sera pas possible d'avoir une théorie complète de la gravité quantique sous sa forme actuelle qui inclura à la limite la relativité générale, car les théories physiques ont toujours été ajustées, au cours de leur évolution, sur la base d'essais d'observation ou expérimentaux, et vérifiées par les prédictions effectuées. En outre, contrairement à une opinion répandue et aux programmes en cours concernant l'unification de toutes les forces fondamentales de la physique dans une théorie finale unique, basée sur la théorie des cordes, je soutiens que cette unification est généralement improbable et, de toute façon, impossible pour que l'unification soit développée sur la base des théories actuelles de la gravité quantique, y compris la théorie des cordes. En outre, je partage l’avis de certains scientifiques et philosophes selon lequel on consacre actuellement trop de ressources à l’idée de développer des théories de la gravité quantique, et en particulier de la théorie des cordes, qui devrait inclure la relativité générale et unifier la gravité avec d’autres forces, en particulier conditions dans lesquelles la science n’impose pas de tels programmes de recherche.

Squeezing of the Super-Elastic Double-Helix Photon in the Gravitational Field (Hidden in Very-Well Known Old Formulae). Pound - Rebka - Snider Effect Studied by the Advanced LIGO Instrument, Pioneer Anomaly and CMB (Cosmic Microwave Background) (23.11.201

Article

Full-text available

Dec 2019

Jiří Stávek

In our approach we have combined knowledge of Old Masters (working in this field before the year 1905), New Masters (working in this field after the year 1905) and Dissidents under the guidance of Louis de Broglie and David Bohm. Based on the great experimental work of Robert Pound, Glen A. Rebka and J.L. Snider we have proposed a squeezing of the super-elastic double-helix photon in the gravitational field. We have newly defined the squeeze rate of that photon particle on the helical path. We have inserted this squeeze rate into the very-well old formulae of Newton, Soldner, Gerber and Einstein and might glimpse traces of the quantum gravity. The squeeze rate of photons can be studied in details using the Great instrument - the Advanced LIGO - located on the surface of the Earth (USA, Italy, Japan). The observed strains on the level 5*10-19 should be caused by the gravitational field of our Earth. The observed strains on the level 5*10-22 should be caused by the gravitational fields of the Moon and the Sun. We estimate that the experimental value of the gravitational constant G studied by the LIGO instrument can achieve the accuracy to the level of ppb (parts per billion) after the removal of those strains from the measured signal and the removal of the gravitational influences of the Earth, the Moon, the Sun, Venus and Jupiter. To study the squeeze effect on a bigger scale we propose to analyze the Pioneer anomaly where Pioneer´s photons have been flying around the planets in our Solar system causing the squeeze effect - the anomalous blueshift. Similarly, we can study cosmic microwave photons flying around the objects in our Solar system that might create “the axis of evil” - temperature fluctuations in the CMB map (Wien displacement law). Can we prepare in our Solar system “tired” light by frequent blueshift - redshift transitions? Can it be that Nature cleverly inserted the squeeze rate into our very-well known Old Formulae? We want to pass this concept into the hands of Readers of this Journal better educated in the Mathematics and Physics.

Epistemology of experimental gravity - Scientific rationality

Preprint

Full-text available

Nov 2019

Nicolae Sfetcu

The evolution of gravitational tests from an epistemological perspective framed in the concept of rational reconstruction of Imre Lakatos, based on his methodology of research programmes. Unlike other works on the same subject, the evaluated period is very extensive, starting with Newton's natural philosophy and up to the quantum gravity theories of today. In order to explain in a more rational way the complex evolution of the gravity concept of the last century, I propose a natural extension of the methodology of the research programmes of Lakatos that I then use during the paper. I believe that this approach offers a new perspective on how evolved over time the concept of gravity and the methods of testing each theory of gravity, through observations and experiments. I argue, based on the methodology of the research programmes and the studies of scientists and philosophers, that the current theories of quantum gravity are degenerative, due to the lack of experimental evidence over a long period of time and of self-immunization against the possibility of falsification. Moreover, a methodological current is being developed that assigns a secondary, unimportant role to verification through observations and/or experiments. For this reason, it will not be possible to have a complete theory of quantum gravity in its current form, which to include to the limit the general relativity, since physical theories have always been adjusted, during their evolution, based on observational or experimental tests, and verified by the predictions made. Also, contrary to a widespread opinion and current active programs regarding the unification of all the fundamental forces of physics in a single final theory, based on string theory, I argue that this unification is generally unlikely, and it is not possible anyway for a unification to be developed based on current theories of quantum gravity, including string theory. In addition, I support the views of some scientists and philosophers that currently too much resources are being consumed on the idea of developing quantum gravity theories, and in particular string theory, to include general relativity and to unify gravity with other forces, as long as science does not impose such research programs.

Copernicus and the Hypothetico-Deductive Method of Correspondence Thinking

Article

Full-text available

Jan 1996

Michal Kokowski

This article is a development of my earlier papers entitled “Copernicus’ correspondence thinking” and “Copernicus’ astronomical works — A remarkable case of applying the methodological idea of correspondence” which were delivered at the XIXth International Congress of History of Science (22-29.08.1993, Zaragoza, Spain) and 10th International Congress of Logic, Methodology and Philosophy of Science (19-25.08.1995 Florence, Italy). To avoid misunderstandings at the very beginning of this article, let us explain here, that the term the ‘correspondence thinking’ has for us a special, methodological character that is closely connected, among other things, with the process of framing by theorists the theories which are linked by the correspondence principle. Regarding the linguistic form, the term ‘correspondence thinking" is comprehended by us as equivalent to Feyerabend’s German term “Korrespondenzdenken” that denotes the sort of thinking of Bohr, Kramers and Heisenberg, which was centered on Bohr’s correspondence principle (see Feyerabend [1962a] p. 203, p. 254 fn. 2). However, the term the ‘correspondence thinking’ will be comprehended by us in the broader sense on which we will say more below.

A Mote in Andromeda's Disk: a Misidentified Periodic AGN Behind M31

Article

Apr 2017
ASTROPHYS J

We identify an object previously thought to be a star in the disk of M31, J0045+41, as a background

z\approx0.215

AGN seen through a low-absorption region of M31. We present moderate resolution spectroscopy of J0045+41 obtained using GMOS at Gemini-North. The spectrum contains features attributable to the host galaxy. We model the spectrum to estimate the AGN contribution, from which we estimate the luminosity and virial mass of the central engine. We also detect \ion{Na}{1} absorption in the Milky Way restframe. We search for evidence of periodicity using g-band photometry from the Palomar Transient Factory and find evidence for a 355 day period. If this signal arises due to the orbit of a binary supermassive black hole system, the system is well within the gravitational wave regime. We calculate the time until inspiral due to gravitational radiation, assuming reasonable values of the mass ratio of the two black holes. We discuss the implications of our findings and forthcoming work to identify other such interlopers.

The Milky Way’s Supermassive Black Hole: How Good a Case Is It?: A Challenge for Astrophysics & Philosophy of Science

Article

Full-text available

Mar 2017

The compact and, with about 4.3+-0.3 million solar masses, very massive object located at the center of the Milky Way is currently the very best candidate for a supermassive black hole (SMBH) in our immediate vicinity. If SgrA* is indeed a SMBH it will, in projection onto the sky, have the largest event horizon and will certainly be the first and most important target for Very Long Baseline Interferometry (VLBI) observations currently being prepared by the Event Horizon Telescope (EHT). These observations in combination with the infrared interferometry experiment GRAVITY at the Very Large Telescope Interferometer (VLTI) and other experiments across the electromagnetic spectrum might yield proof for the presence of a black hole at the center of the Milky Way. This manuscript reviews the observational facts, theoretical grounds and conceptual aspects for the case of SgrA* being a black hole. We treat theory and observations in the framework of the philosophical discussions about "(Anti)Realism and Underdetermination", as this line of arguments allows us to describe the situation in observational astrophysics with respect to supermassive black holes. Questions concerning the existence of supermassive black holes and in particular SgrA* are discussed using causation as an indispensable element. We show that the results of our investigation are convincingly mapped out by this combination of concepts.

Gravitational Wave Astronomy

Chapter

Dec 2017

R. Poggiani

The direct detection of gravitational waves announced on 11 February 2016 has opened a new window onto the universe. The gravitational wave spectrum extends from some nHz to several kHz. This chapter will firstly discuss the acoustic detectors, the first historically developed. The laser interferometric detectors that have performed the discovery are described, together with the main noise sources: shot noise, thermal noise and seismic noise. Ground based interferometers are sensitive from a few Hz to some kHz, while space based interferometers are sensitive in the subHz region.

A Brief History of Gravitational Waves

Article

Full-text available

Sep 2016

This review describes the discovery of gravitational waves. We recount the journey of predicting and finding those waves, since its beginning in the early twentieth century, their prediction by Einstein in 1916, theoretical and experimental blunders, efforts towards their detection, and finally the subsequent successful discovery.

The Discovery of Space-time Tunnels

Chapter

Jan 1991

Barry Parker

We have seen that matter curves the space around it and that the greater the amount of matter, the greater the curvature. But how extreme can the curvature become? Is it possible for matter to create an infinite curvature? This possibility bothered Einstein and others after the first solution of the field equations of general relativity was found. Indeed, a mystery developed that was not cleared up for over 40 years. It was, however, the final resolution of this mystery that now forms the basis of our hope for space travel.