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Book Review: Three roads to quantum gravity / Basic Books, 2001
... The most followed approach for experimental search of Quantum Gravity (QG) is probably to test Lorentz Invariance Violation (LIV) [1][2][3]. A very generic and model-independent formalism to achieve this goal consists in writing the dispersion relations as a series expansion of the form ...
... Since E QG is much higher than the energy of all gamma-ray photons observed, the lowest order term dominates in Eq. (1). At present day, only the n¼ 1 and n ¼2 orders can be constrained with good sensitivity. ...
Because they are bright and distant, Gamma-ray Bursts (GRBs) have been used for more than a decade to test propagation of photons and to constrain relevant Quantum Gravity (QG) models in which the velocity of photons in vacuum can depend on their energy. With its unprecedented sensitivity and energy coverage, the Fermi satellite has provided the most constraining results on the QG energy scale so far. In this talk, the latest results obtained from the analysis of four bright GRBs observed by the Large Area Telescope will be reviewed. These robust results, cross-checked using three different analysis techniques set the limit on QG energy scale at E>7.6 times the Planck energy for linear dispersion and E>1.3×1011 GeV for quadratic dispersion (95% CL). After describing the data and the analysis techniques in use, results will be discussed and confronted to latest constraints obtained with Active Galactic Nuclei.
... The possibility of a deformation in the dispersion relation of microscopic particles, appears in connection with the quest for a quantum theory of gravity [1] [2] [3] [4] [5] [6] [7] [8] [9]. This entails, in some schemes, that a possible spacetime quantization has as a consequence a modification of the classical–spacetime dispersion relation between energy E and (modulus of) momentum p of a microscopic particle with mass m [2] [3] [5]. ...
... The three parameters ξ 1 , ξ 2 , and ξ 3 , are model dependent [2] [5], and should take positive or negative values close to 1. There is some evidence within the formalism of Loop quantum gravity [5] [6] [7] [8] that indicates non–zero values for the three parameters, ξ 1 , ξ 2 , ξ 3 , and particulary that produces a linear–momentum term in the non–relativistic limit [7] [9]. ...
We analyze the consequences caused by an anomalous single-particle dispersion relation sug- gested in several quantum-gravity models, upon the thermodynamics of a Bose–Einstein condensate trapped in a generic 3-dimensional power-law potential. We prove that the condensation tempera- ture is shifted as a consequence of such deformation and show that this fact could be used to provide bounds on the deformation parameters. Additionally, we show that the shift in the condensation temperature, described as a non-trivial function of the number of particles and the trap parameters, could be used as a criterion to analyze the effects caused by a deformed dispersion relation in weakly interacting systems and also in finite size systems.
... There can be no unentailed events, so emergence is just wrong and there must be a final theory 'down there' from which all derives by entailment. As Weinberg famously says, (10), the explanatory arrows all point downward, from societies to people to organs to cells to biochemistry to chemistry to physics and ultimately to particle physics and General Relativity, or perhaps String Theory, (12). Turing-Church-Deutsch holds precisely the same view -it is algorithms all the way down so entailment all the way up. ...
... All other Aristotelian causes were banished from science. This banishment, this view that all that happens in the universe is to be explained by deduction, lies at the base of our long love of reductionism, Weinberg's dream of a final theory, (10), and current string theory, (12). If all explanation is by logical entailment, then we reason that there must be a final theory of everything at the base of physics that entails logically all that unfolds in the universe. ...
Since Descartes' dualism, with his res extensa and res cogitans, six fundamental problems in the philosophy and natural history of mind are these: 1. how does mind act on matter? 2. If mind does not act on matter is mind a mere epiphenomenon? 3. What might be the source of free will? 4. What might be the source of a responsible free will? 5. Why might it have been selectively advantageous to evolve consciousness? 6. What is consciousness? I approach the first five of the above six problems based on two physical postulates. First the mind-brain system is a quantum coherent, but reversibly decohering and recohering system. This allows me to answer 1) above, mind does not act causally on brain at all, rather it acausally decohers to classicity (for all practical purposes), hence has consequences for brain and body as matter. Epiphenomenalism is averted. A quantum mind, because it is acausal on Copenhagen including Born, yields a free will, but a merely random free will, not a responsible free will. Second, the most radical part of this article proposes that the quantum classical interface is not always describable by a law: specifically in a special relativity setting, no function, F, maps the present state of the system mind-brain into its future. In its place is a nonrandom yet lawless process. I seek in this non-random yet lawless process a source for a responsible free will. Finally, if the quantum-classical boundary can be non-random yet lawless, then no algorithmic simulation of the world or ourselves can calculate the real world, hence the evolutionary selective advantages for evolving consciousness to know it may be great. I make no progress on problem 6, the hard problem of qualia.
... There are many attempts to link General Relativity Theory (GRT) with Quantum Mechanics (QM) and search for Quantum Gravity[1],[2],[3],[4],[5],[6],[7],[8]. Some authors are developing GRT, some are contradicting, others concentrate on quantization problem. ...
In the article it is proved, that from de Broglie hypothesis one may derive, that four-acceleration A, four-velocity U and four-position X are linked into one AUX equation EA - SU = mX where S denotes action and E is related to the energy of a field. This finding gives exact metric formulation for non-inertial systems and brings important consequences for many research areas of physics.
... The DP version of OR involves a different interpretation of the term 'quantum gravity' from what is usual. Current ideas of quantum gravity (see, for example, Smolin [120]) normally refer, instead, to some sort of physical scheme that is to be formulated within the bounds of standard quantum field theory—although no particular such theory, among the multitude that has so far been put forward, has gained anything approaching universal acceptance, nor has any of them found a fully consistent, satisfactory formulation. 'OR' here refers to the alternative viewpoint that standard quantum (field) theory is not the final answer, and that the reduction R of the quantum state ('collapse of the wavefunction') that is adopted in standard quantum mechanics is an actual physical process which is not part of the conventional unitary formalism U of quantum theory (or quantum field theory). ...
The nature of consciousness, the mechanism by which it occurs in the brain, and its ultimate place in the universe are unknown. We proposed in the mid 1990's that consciousness depends on biologically 'orchestrated' coherent quantum processes in collections of microtubules within brain neurons, that these quantum processes correlate with, and regulate, neuronal synaptic and membrane activity, and that the continuous Schrödinger evolution of each such process terminates in accordance with the specific Diósi-Penrose (DP) scheme of 'objective reduction' ('OR') of the quantum state. This orchestrated OR activity ('Orch OR') is taken to result in moments of conscious awareness and/or choice. The DP form of OR is related to the fundamentals of quantum mechanics and space-time geometry, so Orch OR suggests that there is a connection between the brain's biomolecular processes and the basic structure of the universe. Here we review Orch OR in light of criticisms and developments in quantum biology, neuroscience, physics and cosmology. We also introduce a novel suggestion of 'beat frequencies' of faster microtubule vibrations as a possible source of the observed electro-encephalographic ('EEG') correlates of consciousness. We conclude that consciousness plays an intrinsic role in the universe.
... Fortunately, it is not necessary to worry about the details of possible nonlinear or stochastic additions to the Schrödinger equation, which might embody the coarsegrained effects of a deeper theory, say, incorporating gravitation or a granular space-time [13] [14] [15], or might represent a fundamental stochasticity [16] [17] [18]. All that matters empirically are their observable consequences, described by the dynamics of the many-body density operator. ...
We propose an experimentally accessible, objective measure for the macroscopicity of superposition states in mechanical quantum systems. Based on the observable consequences of a minimal, macrorealist extension of quantum mechanics, it allows one to quantify the degree of macroscopicity achieved in different experiments.
... Indeed, BECs are of interest in the context of quantum gravity. In Refs.[42] [43] some of us have shown that Planck-scale deformations of the energy-momentum relation that naturally emerges in many quantum-gravity theories (for an excellent nontechnical overview see Ref.[44]) may affect the properties of low-temperature BECs. In particular it was shown that a Planck-scale induced deformation of the Minkowski energy-momentum dispersion relation E ≃ m 2 c 4 + p 2 c 2 + ξ m c p/2M p , where m is the mass of the bosons, M p the Planck mass and ξ a dimensionless parameter, produces a shift in the condensation temperature T c of about ∆T c /T 0 c ≃ 10 −6 ξ 1 in typical BECs such as 87 37 Rb [31], 7 3 Li [32], 23 11 Na [33], 1 1 H [34], 85 37 Rb [35], 4 2 He [36], 41 19 K [37], 133 55 Cs [38], and 52 24 Cr [39]. ...
A relativistic complex scalar boson field at finite temperature T is
examined below its critical Bose-Einstein condensation temperature. It is shown
that at the same T the state with antibosons has higher entropy, lower
Helmholtz free energy and higher pressure than the state without antibosons,
but the same Gibbs free energy as it should. This implies that the
configuration without antibosons is metastable. Results are generalized for
arbitrary d spatial dimensions.
... One of the consequences of LI is that the speed of light is constant and, in particular, that it does not depend on the photon energy. If, however, spacetime has structure , like it is postulated in some approaches to combine quantum mechanics and general relativity [1] [2], it could be that the speed of light depends on the energy of the photon . From our everyday experience we know that the effect , if it exists, is very small and, therefore, only evident if the energy of the photons is in the gamma-ray regime and the photons have traveled large distances. ...
Gamma-ray observations provide sensitive tests of Lorentz invariance
violation (LIV). At present the most sensitive tests come from observations of
transient events, gamma-ray bursts and flaring AGN. Disadvantages of transients
are that an independent confirmation by a different experiment is often not
possible and that limits cannot be improved with a longer exposure. Pulsars do
not have these disadvantages. Testing Lorentz invariance with pulsars was not
considered seriously so far because limits were not competitive. The VERITAS
collaboration has recently reported the detection of pulsed emission from the
Crab pulsar above 100 GeV. This measurement can be used to constrain LIV
effects with a sensitivity that is competitive with some of the best available
limits. In view of this unexpected result we discuss what the prospects are of
doing LIV tests with very-high energy gamma-ray emission from pulsars.
... . The theory of Quantum Gravity (see e.g. [3]), which is still incomplete, would give a unified picture based on both Quantum Mechanics and General Relativity, thus leading to a common description of the four fundamental forces. Quantum Gravity effects in the framework of String Theory [4], where the gravitation is considered as a gauge interaction, result from a graviton-like exchange in a classical space-time. ...
Several models of Quantum Gravity predict Lorentz Symmetry breaking at energy scales approaching the Planck scale (10^{19} GeV). With present photon data from the observations of distant astrophysical sources, it is possible to constrain the Lorentz Symmetry breaking linear term in the standard photon
dispersion relations. Gamma-ray Bursts (GRB) and flaring Active Galactic Nuclei (AGN) are complementary to each other for this purpose, since they are observed at different distances in different energy ranges and with different levels of variability. Following a previous publication of the High Energy Stereoscopic System (H.E.S.S.) collaboration, a more sensitive event-by-event method consisting of a likelihood fit is applied to PKS 2155-304 flare data of MJD 53944 (July 28, 2006) as used in the previous publication. The previous limit on the linear term is improved by a factor of ~3 up to M^{l}_{QG} > 2.1x10^{18} GeV and is currently the best result obtained with blazars. The sensitivity to the quadratic term is lower and provides a limit of M^{q}_{QG} > 6.4x10^10 GeV, which is the best value obtained so far with an AGN and similar to the best limits obtained with GRB.
The constant of gravitational freedom of empty space is inferred through a completion of the symmetry between Coulomb force and gravitational force equations. I suggest that gravitational freedom of empty space is the 3D equivalent of 2D electric permittivity of empty space and 1D magnetic permeability of empty space. The present value of electric permittivity must be corrected to account for gravitational freedom of empty space, which fits naturally into the speed of light equation.
We discuss the consequences of a duality-invariant Einstein-Planck relation
on the equation of state of micro black holes. The results are analogous to
those obtained from the "world crystal" model, but with some significative
differences, as for instance a limiting vanishing value for temperature for
very small black holes. The model leads to a total evaporation of micro black
holes but with the final stage being very slow.
We propose a generalized Einstein-Planck relation for photons which is invariant under the change λ/alP to alP/λ, λ being the photon wavelength, lP Planck’s length, and a a numerical constant. This yields a wavelength-dependent speed of light v(λ)=c/(1+a2(lP/λ)2), with c the usual speed of light in vacuo, indicating that the speed of light should decrease for sufficiently short wavelengths. We discuss the conceptual differences with the previous proposals related to a possible decrease of the speed of light for very short wavelengths based on quantum fluctuations of the space-time, as well as its consequences on Heisenberg’s uncertainty principle up to second order in lP.
We analyze the consequences caused by a deformed dispersion relation,
suggested in several quantum gravity models, upon a bosonic gas. Concerning the
ground state of the Bogoliubov space of this system, we deduce the corrections
in the pressure, the speed of sound, and the corresponding healing length.
Indeed, we prove that the corrections in the relevant thermodynamic properties
associated with the ground state, defines a non trivial function of the density
of particles and the deformation parameters, allowing us to constrain, in
principle, the form of the modified energy-momentum dispersion relation.
Underlying any theory of physics is a layer of conceptual frames. They connect the mathematical structures used in theoretical models with physical phenomena, but they also constitute our fundamental assumptions about reality. Many of the discrepancies between quantum physics and classical physics (including Maxwell's electrodynamics and relativity) can be traced back to these categorical foundations. We argue that classical physics corresponds to the factual aspects of reality and requires a categorical framework which consists of four interdependent components: boolean logic, the linear-sequential notion of time, the principle of sufficient reason, and the dichotomy between observer and observed. None of these can be dropped without affecting the others. However, in quantum theory the reduction postulate also addresses the "status nascendi" of facts, i.e., their coming into being. Therefore, quantum phyics requires a different conceptual framework which will be elaborated in this article. It is shown that many of its components are already present in the standard formalisms of quantum physics, but in most cases they are highlighted not so much from a conceptual perspective but more from their mathematical structures. The categorical frame underlying quantum physics includes a profoundly different notion of time which encompasses a crucial role for the present. Comment: 35 pages, 1 figure
A non-Abelian, Universal SpaceTime Ontology is introduced in terms of Categories, Functors, Natural Transformations, Higher
Dimensional Algebra and the Theory of Levels. A Paradigm shift towards Non-Commutative Spacetime structures with remarkable
asymmetries or broken symmetries, such as the CPT-symmetry violation, is proposed. This has the potential for novel applications
of Higher Dimensional Algebra to SpaceTime structure determination in terms of universal, topological invariants of ‘hidden’
symmetry. Fundamental concepts of Quantum Algebra and Quantum Algebraic Topology, such as Quantum Groups, von Neumann and
Hopf Algebras are first considered with a view to their possible extensions and future applications in Quantum Field theories.
New, non-Abelian results may be obtained through Higher Homotopy, General van Kampen Theorems, Lie Groupoids/Algebroids and
Groupoid Atlases, possibly with novel applications to Quantum Dynamics and Local-to-Global Problems, Quantum Logics and Logic
Algebras. Many-valued Logics, Łukasiewicz–Moisil Logics lead to Generalized LM-Toposes as global representations of SpaceTime
Structures in the presence of intense Quantum Gravitational Fields. Such novel representations have the potential to develop
a Quantum/General Relativity Theory in the context of Supersymmetry, Supergravity, Supersymmetry Algebras and the Metric Superfield
in the Planck limit of spacetime. Quantum Gravity and Physical Cosmology issues are also considered here from the perspective
of multiverses, thus leading also to novel types of Generalized, non-Abelian, Topological, Higher Homotopy Quantum Field Theories
(HHQFT) and Non-Abelian Quantum Algebraic Topology (NA-QAT) theories.
The Veterans Health Administration patient safety reporting system receives more than 100,000 reports annually. The information contained in these reports is primarily in the form of natural language text. Improving the ability to efficiently mine these patient safety reports for information is the objective of a proposed semi-supervised method.
A semi-supervised classification method leverages information from both labeled and unlabeled reports to predict categories for the unlabeled reports.
Two different scenarios involving a semi-supervised learning process are examined, and both demonstrate good predictive results.
The semi-supervised method shows much promise in assisting researchers and analysts toward accurately and more quickly separating reports of varying and often overlapping topics. The method is able to use the "stories" provided in patient safety reports to extend existing patient safety taxonomies beyond their static design.
The accepted structure of space and vacuum derives from the results of relativistic cosmology and quantum field theory. It is demonstrated that a chiral interface between enantiomeric regions of a closed universe, or a (right) R-Universe and (left) L-Universe, related by an element of PCT symmetry along the intarface, represents a construct with all the attributes required of the theoretical vacuum, in-so-far as quantum behaviour is then seen to be induced by the vacuum interface. Quantum mechanics emerges as a special case of classical mechanics, rather than the latter being a subset of the former. This removes the quantum-mechanical observational problem, explains the cosmological large-number coincidences, and accounts for the anti-matter in the cosmos.
Assuming the holographic principle, the gravitational force can be formulated thermodynamically as an entropic force, but the mechanism by which the attraction between two masses occurs is not clear. The physical basis for the holographic principle is also unknown. My primary assumption is that empty space consists of discrete countable units that have on the order of one bit of entropy per cubic Planck unit. The basic idea here is simply that rather than matter just occupying empty space, the presence of matter excludes discrete units of space that have entropy. I argue that this volume exclusion of empty space leads to an attractive gravitational force and to the holographic principle. Comment: 10 pages, 2 figures
The purpose of the following paper is to demonstrate that the "limits of physics" are in a very important way determined by the conceptual framework and language of discourse that we use to describe physical reality. In this paper we examine three areas where the structure of discourse has been particularly difficult. In this regard we examine three problems, the problem of time (which is discussed in two sections of the paper), the problem of non-locality in quantum mechanics and some related general difficulties of interpretation specific to the Copenhagen school, and the concept of maximality as it is employed with respect to cosmic inflation in general relativity and quantum cosmology. Comment: 8 pages
Since time immemorial, philosophers and scientists were searching for a “machine code” of the so-called Mentalese language capable of processing information at the pre-verbal, pre-expressive level. In this paper I suggest that human languages are only secondary to the system of primitive extra-linguistic signs which are hardwired in humans and serve as tools for understanding selves and others; and creating meanings for the multiplicity of experiences. The combinatorial semantics of the Mentalese may find its unorthodox expression in the semiotic system of Tarot images, the latter serving as the ”keys” to the encoded proto-mental information. The paper uses some works in systems theory by Erich Jantsch and Erwin Laszlo and relates Tarot images to the archetypes of the field of collective unconscious posited by Carl Jung. Our subconscious beliefs, hopes, fears and desires, of which we may be unaware at the subjective level, do have an objective compositional structure that may be laid down in front of our eyes in the format of pictorial semiotics representing the universe of affects, thoughts, and actions. Constructing imaginative narratives based on the expressive “language” of Tarot images enables us to anticipate possible consequences and consider a range of future options. The thesis advanced in this paper is also supported by the concept of informational universe of contemporary cosmology.
The accepted structure of space and vacuum derives from the results of relativistic cosmology and quantum field theory. It is demonstrated that a chiral interface between enantiomeric regions of a closed universe, or a (right) R-Universe and (left) L-Universe, related by an element of PCT symmetry along the interface, represents a construct with all the attributes required of the theoretical vacuum, in-so-far as quantum behaviour is then seen to be induced by the vacuum interface. Quantum mechanics emerges as a special case of classical mechanics, rather than the latter being a subset of the former. This removes the quantum-mechanical observational problem, explains the cosmological large-number coincidences, and accounts for the anti-matter in the cosmos La estructura aceptada del espacio y el vacío se derivan de los resultados de la cosmología relativística y de la teoría cuántica de campo. Se demuestra que una interfaz quiral entre regiones enantioméricas de un universo cerrado, o un universo derecho y un universo izquierdo, relacionados por un elemento de simetría PCT a lo largo de la interfaz, representa un modelo con todos los atributos requeridos por el vacío teórico. Se desprende que el comportamiento cuántico es entonces visto que es inducido por la interfaz de vacío. La mecánica quántica emerge como un caso especial de la mecánica clásica, más bien que siendo la última un subconjunto de la primera. Esto resuelve el problema observacional mecánico cuántico, explica las coincidencias de los grandes números cosmológicos y toma en cuenta la antimateria en el cosmos
Extending along the dynamic continuum from conflict to cooperation, microbial infections always involve symbiosis (Sym) and pathogenesis (Pat). There exists a dynamic Sym-Pat duality (DSPD) in microbial infection that is the most fundamental problem in infectomics. DSPD is encoded by the genomes of both the microbes and their hosts. Three focal point (FP) theory-based game models (pure cooperative, dilemma, and pure conflict) are proposed for resolving those problems. Our health is associated with the dynamic interactions of three microbial communities (nonpathogenic microbiota (NP) (Cooperation), conditional pathogens (CP) (Dilemma), and unconditional pathogens (UP) (Conflict)) with the hosts at different health statuses. Sym and Pat can be quantitated by measuring symbiotic index (SI), which is quantitative fitness for the symbiotic partnership, and pathogenic index (PI), which is quantitative damage to the symbiotic partnership, respectively. Symbiotic point (SP), which bears analogy to FP, is a function of SI and PI. SP-converting and specific pathogen-targeting strategies can be used for the rational control of microbial infections.
The development of quantum information theory has renewed interest in the idea that the state vector does not represent the state of a quantum system, but rather the knowledge or information that we may have on the system. I argue that this epistemic view of states appears to solve foundational problems of quantum mechanics only at the price of being essentially incomplete. Comment: Clarifications in Sec. 2. To appear in Found. Phys
In relativistic theories, the assumption of proper mass constancy generally holds. We study gravitational relativistic mechanics of point particle in the novel approach of proper mass varying under Minkowski force action. The motivation and objective of this work are twofold: first, to show how the gravitational force can be included in the Special Relativity Mechanics framework, and, second, to investigate possible consequences of the revision of conventional proper mass concept (in particular, to clarify a proper mass role in the divergence problem). It is shown that photon motion in the gravitational field can be treated in terms of massless refracting medium, what makes the gravity phenomenon compatible with SR Mechanics framework in the variable proper mass approach.
Specifically, the problem of point particle in the spherical symmetric stationary gravitational field is studied in SR-based Mechanics, and equations of motion in the Lorentz covariant form are obtained in the relativistic Lagrangean problem formulation. The dependence of proper mass on potential field strength is derived from the Euler-Lagrange equations as well. One of new results is the elimination of conventional 1/r divergence, which is known to be not removable in Schwarzschild gravitomechanics. Predictions of particle and photon gravitational properties are in agreement with GR classical tests under weak-field conditions; however, deviations rise with potential field strength. The conclusion is made that the approach of field-dependent proper mass is perspective for development of SR gravitational mechanics and further studies of gravitational problems.
Based on the model of Expansive Nondecelerative Universe, the aim of the present contribution is to contribute to the theoretical rationalization of some experiments, in particular of those performed by Podkletnov and de Aquino and devoted to the gravitational mass cessation, to offer a mechanistic explanation of the Solar corona heating, and to propose an experiment to verify the explanation of the heating in the Earth conditions.
I present a non-technical and necessarily biased and incomplete overview of our present understanding of the physical universe and its constituents, emphasizing what we have learned from the explosive growth in cosmological and astrophysical data acquisition and some of the key open questions that remain. The topics are organized under the labels space, time, and matter. Most bibliographical references are for the non-expert. Comment: 5 pages, LaTeX. Keynote address at the International Workshop on Astronomy and Relativistc Astrophysics, October 12-16, Olinda, Brazil. To be published in the proceedings (Int. J. Mod. Phys. D)
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