Vesselin G. Gueorguiev

Ronin Institute for Independent Scholarship

On the basis of a general action principle, we revisit the scale invariant field equation using the cotensor relations by Dirac (1973). This action principle also leads to an expression for the scale factor λ, which corresponds to the one derived from the gauging condition, which assumes that a macroscopic empty space is scale-invariant, homogeneou...

We summarize the main results within the Scale Invariant Vacuum (SIV) paradigm as related to the Weyl Integrable Geometry (WIG) as an extension to the standard Einstein General Relativity (EGR). After a short sketch of the mathematical framework, the main results until 2023 [1] are highlighted in relation to: the inflation within the SIV [2], the g...

The Scale Invariant Vacuum (SIV) paradigm is applied to the Big-Bang Nucleosynthesis using the known analytic expressions for the expansion factor $a$ and the plasma temperature $T$ as functions of the SIV time $\tau$ since the Big-Bang when $a(\tau=0)=0$. The results are compared to the known standard BBNS model as calculated with the PRIMAT code....

Main Conference presentation on SIV for a few Summer 2022 & 2023 conferences: (*) ХХIII International Meeting Physical Interpretations of Relativity Theory (PIRT- 2023) at the Bauman Moscow State Technical University , 3-6 July 2023 (https://pirt.bmstu.ru/en/scientific-program-en/); (*) Modern Cosmology - Spontaneous Workshop (SW XIV) in IESC Carge...

Talk on the Big-Bang Nucleosynthesis within the Scale Invariant Vacuum Paradigm. Abstract: The Scale Invariant Vacuum (SIV) paradigm is applied to the Big-Bang Nucleosynthesis using the known analytic expressions for the expansion factor a and the plasma temperature T as functions of the SIV time τ since the Big-Bang when a(τ = 0) = 0. The results...

Slides for the 2023 APS April meeting presentation on "The Big-Bang Nucleosynthesis (BBNS) within the Scale-Invariant Vacuum (SIV) paradigm" Presented in person in session H14 on 16th of April 2023, in Minneapolis, Minnesota; and virtually in session GG02 on 24th of April 2023. Abstract: The Scale Invariant Vacuum (SIV) paradigm is applied to the...

In preparation for the 2023 NSAC Long Range Plan (LRP), members of the Nuclear Science community gathered to discuss the current state of, and plans for further leveraging opportunities in, QIST in NP research at the Quantum Information Science for U.S. Nuclear Physics Long Range Planning workshop, held in Santa Fe, New Mexico on January 31 - Febru...

The author discusses some of the challenges that future nuclear modeling may face in order to improve the description of the nuclear structure. One challenge is related to the need for A-body nuclear interactions justified by various contemporary nuclear physics studies. Another challenge is related to the discrepancy in the NNN contact interaction...

Slides of the talk presented at the LOOPS'22 in Lyon https://indico.cern.ch/event/1100970/

Scale invariance is expected in empty Universe models, while the presence of matter tends to suppress it. As shown recently, scale invariance is certainly absent in cosmological models with densities equal to or above the critical value $\varrho_{\mathrm{c}} =3H^2_0/(8 \pi G)$. For models with densities below $\varrho_{\mathrm{c}}$, the possibility...

We present a summary of the main results within the Scale Invariant Vacuum (SIV) paradigm as related to the Weyl Integrable Geometry (WIG) as an extension to the standard Einstein General Relativity (EGR). After a brief review of the mathematical framework, we will highlight the main results related to inflation within the SIV, the growth of the de...

We present a summary of the main results within the Scale Invariant Vacuum (SIV) paradigm as related to the Weyl Integrable Geometry. After a brief review of the mathematical framework, we will highlight the main results related to inflation within the SIV [9], the growth of the density fluctuations [8], and the application of the SIV to scale-inva...

Recently it was found from Cassini data that the mean recession speed of Titan from Saturn is v = 11.3 ± 2.0 cm/yr which corresponds to a tidal quality factor of Saturn Q ≈ 100 while the standard estimate yields Q ≥ 6 · 104 . It was assumed that such a large speed v is due to a resonance locking mechanism of five inner mid-sized moons of Saturn. In...

We review the problem of the consistency between the observed values of the lunar recession from Lunar Laser Ranging (LLR) and of the increase of the length-of-the-day (LOD). From observations of lunar occultations completed by recent IERS data, we derive a variation rate of the LOD equal to 1.09 ms/cy from 1680 to 2020, which compares well with Mc...

We review the problem of the consistency between the observed values of the lunar recession from Lunar Laser Ranging (LLR) and of the increase of the length-of-the-day (LOD). From observations of lunar occultations completed by recent IERS data, we derive a variation rate of the LOD equal to 1.09 ms/cy from 1680 to 2020, which compares well with Mc...

Maxwell equations and the equations of General Relativity are scale-invariant in empty space. In the present approach, we identify the scalar field of the empty space in the Scale Invariant Vacuum (SIV) context to the scalar field φ in the energy density ρ = (1/2)(dφ/dt)^2 +V(φ) of the vacuum at inflation. This leads to some constraints on the pote...

The talk discusses some of the challenges for nuclear modeling in order to improve the description of the nuclear structure. One challenge is related to the need for A-body nuclear interactions justified by various contemporary nuclear physics studies. Another challenge is related to the discrepancy in the NNN contact interaction parameters for 3He...

Maxwell equations and the equations of General Relativity are scale invariant in empty space. The presence of charge or currents in electromagnetism or the presence of matter in cosmology are preventing scale invariance. The question arises on how much matter within the horizon is necessary to kill scale invariance. The scale invariant field equati...

Maxwell equations and the equations of General Relativity are scale invariant in empty space. The presence of charge or currents in electromagnetism or the presence of matter in cosmology are preventing scale invariance. The question arises on how much matter within the horizon is necessary to kill scale invariance. The scale invariant field equati...

In this paper, we argue in favor of first-order homogeneous Lagrangians in the velocities. The relevant form of such Lagrangians is discussed and justified physically and geometrically. Such Lagrangian systems possess Reparametrization Invariance (RI) and explain the observed common Arrow of Time as related to the non-negative mass for physical par...

Based on the principle of reparametrization invariance, the general structure of physically relevant classical matter systems is illuminated within the Lagrangian framework. In a straightforward way, the matter Lagrangian contains background interaction fields, such as a 1-form field analogous to the electromagnetic vector potential and symmetric t...

Highly excited states in 156Gd, populated via the neutron pickup reaction 157Gd(3He,4He)156Gd, are investigated, and their spin–parity distribution P(Jπ,E) is examined. The cross section for one-neutron transfers to states above the neutron separation energy in 156Gd is calculated as coherent sum, using standard reaction codes that employ spherical...

A new perspective on the Cosmological Constant Problem (CCP) is proposed and discussed within the multiverse approach of Quantum Cosmology. It is assumed that each member of the ensemble of universes has a characteristic scale $a$ that can be used as integration variable in the partition function. An averaged characteristic scale of the ensemble is...

Recent studies in applying the Weyl's original gauge symmetry idea within the framework of the Weyl's Integrable Geometry to modern observational data in cosmology has resulted in the Scale Invariant Vacuum (SIV) paradigm. A sequence of papers by Prof. André Maeder has shown that SIV is a viable contender to standard LamdaCDM model see [1] for rece...

A new perspective on the Cosmological Constant Problem (CCP) is proposed and discussed within the multiverse approach of Quantum Cosmology. It is assumed that each member of the ensemble of universes has a characteristic scale a that can be used as integration variable in the partition function. An averaged characteristic scale of the ensemble is e...

Presentation for the HackerEarth Hackathon - 2020 Qiskit Community Summer Jam - California Section https://www.hackerearth.com/challenges/hackathon/qiskit-community-summer-jam-california/dashboard/0426544/submission/

The oblique basis method is reviewed from engineering point of view related to vibration and control theory. Examples are used to demonstrate and relate the oblique basis in nuclear physics to the equivalent mathematical problems in vibration theory. The mathematical techniques, such as principal coordinates and root locus, used by vibration and co...

Dark matter and dark energy (DE) represent the two most challenging problems of contemporary physics and astrophysics. DM and DE represents 95% of the matter-energy in the universe and they are not understood. Supporting evidence for DM has been obtained from astronomical observations of the rotation curve of galaxies, the growth of the density flu...

The Scale Invariant Vacuum (SIV) theory rests on the basic hypothesis that the macroscopic empty space is scale invariant. This hypothesis is applied in the context of the Integrable Weyl Geometry, where it leads to considerable simplifications in the scale covariant cosmological equations. After an initial explosion and a phase of braking, the cos...

The Scale-Invariant Vacuum (SIV) theory is based on Weyl’s Integrable Geometry, endowed with a gauge scalar field. The main difference between MOND and the SIV theory is that the first considers a global dilatation invariance of space and time, where the scale factor λ is a constant, while the second opens the likely possibility that λ is a functio...

The Scale-Invariant Vacuum (SIV) theory is based on Weyl's Integrable Geometry, endowed with a gauge scalar field. The main difference between MOND and the SIV theory is that the first considers a global dilatation invariance of space and time, where the scale factor $\lambda$ is a constant, while the second opens the likely possibility that $\lamb...

Talk given at the Hacker Dojo, Santa Clara on Nov. 8th, 2019 as part of an event in the "Quantum Computing, AI, and ML" MeetUp group. (https://www.meetup.com/Quantum-Computing-AI-and-ML) Slides (pdf format) available here: https://www.slideshare.net/VGG-Consulting and the Zoom recording of the talk is available on YouTube: https://www.youtube.com/...

Talk presented at the Dark Universe Workshop – Early Universe Cosmology, Baryogenesis and Dark Matter, ICTP-SAIFR, São Paulo, Brazil, October 21-25, 2019. https://www.ictp-saifr.org/dark-universe-workshop-early-universe-cosmology-baryogenesis-and-dark-matter/

Workshop on Quantum Symmetries - October 16-18, 2019, ICTP-SAIFR, São Paulo, Brazil https://www.ictp-saifr.org/workshop-on-quantum-symmetries/ Video recording of the talk available here: https://www.youtube.com/watch?v=aMsIMCsWRrY&feature=youtu.be

The growth of the density fluctuations is considered to be an important cosmological test. In the standard model, for a matter dominated universe, the growth of the density perturbations evolves with redshift z like ([Formula Presented]) s with s=1. This is not fast enough to form galaxies and to account for the observed present-day inhomogeneities...

The relativistic particle Lagrangian justifies the importance of Reparametrization-Invariant Systems - in particular, the first-order homogeneous Lagrangians in the velocities. Such systems are studied from the point of view of the Lagrangian and extended Hamiltonian formalism. The extended Hamiltonian formulation is using an extended Poisson brack...

List of VGG dissemination activities via publications and conference participations.

Based on the principle of Reparametrization Invariance the general structure of physically relevant classical matter systems are illuminated within the Lagrangian framework. The canonical structure of a reparametrization invariant Lagrangian for an extended object (p-brane) embedded in a bulk space M is shown to lead to some familiar Lagrangians, s...

The growth of the density fluctuations is considered to be an important cosmological test. In the standard ΛCDM cosmological model, it is assumed that to form galaxies the baryons settle down in the potential well of dark matter previously assembled during the radiation era of the universe. As such, it has been previously used to infer the presence...

We discuss modeling of nuclear structure beyond the 2-body interaction paradigm. Our first example is related to the need of three nucleon contact interaction terms suggested by chiral perturbation theory. The relationship of the two low-energy effective coupling parameters for the relevant three nucleon contact interaction terms $c_D$ and $c_E$ th...

We study the spin-parity distribution P(J$^{\pi}$,E) of $^{156}$Gd excited states above the neutron separation energy $S_{n}=8.536$ MeV \cite{156Gd_list_of_levels} that are expected to be populated via the 1-step neutron pickup reaction $^{157}$Gd($^{3}$He,$^{4}$He)$^{156}$Gd. In analogy with the rotor plus particle model \cite{Bohr&Mottelson-II},...

The oblique basis method is reviewed from engineering point of view related to vibration and control theory. Examples are used to demonstrate and relate the oblique basis in nuclear physics to the equivalent mathematical problems in vibration theory. The mathematical techniques, such as principal coordinates and root locus, used by vibration and co...

We first review the development of the Richardson-Gaudin exactly-solvable pairing models and then discuss several new models based on rank-two algebras and their applications to problems in nuclear structure.

A mean-field Hamiltonian with an extended pairing interaction that includes multi-pair excitations is proposed for describing strongly-deformed nuclei. Solutions are easily obtained. The results show that even though the theory includes many-body interaction terms, the one- and two-body parts continue to dominate the dynamics for small values of th...

This work discusses the relevance of three Sky Cover (SC) indices for solar radiation modeling and forecasting. The three indices are global in the sense that they integrate relevant information from the whole sky and thus encode cloud cover information. However, the three indices also emphasize different specific meteorological processes and sky r...

Many exactly solvable models are based on Lie algebras. The pairing interaction is important in nuclear physics and its exact solution for identical particles in non-degenerate single-particle levels was first given by Richardson in 1963. His solution and its generalization to Richardson-Gaudin quasi-exactly solvable models have attracted the atten...

We discuss some of the challenges that future nuclear modeling may face in order to improve the description of the nuclear structure. One challenge is related to the need for A-body nuclear interactions justified by various contemporary nuclear physics studies. Another challenge is related to the discrepancy in the NNN contact interaction parameter...

A multiverse approach to the Cosmological Constant Problem (CCP) is considered. It is assumed that each member of the multiverse ensemble has a characteristic scale ’a’ that can be used as integration variable in the partition function. An averaged characteristic scale of an ensemble is estimated by using only members that satisfy the Einstein fiel...

In a previous work [E.M. Prodanov, R.I. Ivanov and V.G. Gueorguiev, Reissner-Nordström expansion, Astropart. Phys. 27 (2007) 150], we proposed a classical model for the expansion of the Universe during the radiation-dominated epoch based on the gravitational repulsion of the Reissner-Nordström geometry — naked singularity description of particles t...

We outline two complementary approaches based on the no core shell model (NCSM) and present recent results. In the ab initio approach, nuclear properties are evaluated with two-nucleon (NN) and three-nucleon interactions (TNI) derived within effective field theory (EFT) based on chiral perturbation theory (ChPT). Fitting two available parameters of...

An extended SU(3) shell model that for the first time explicitly includes unique-parity levels is introduced. Shell-model calculations for the isotopes of $^{64}$Ge and $^{68}$Se are performed where valence nucleons beyond the N=28=Z core occupy levels of the normal parity upper-$fp$ shell ($f_{5/2},p_{3/2},p_{1/2}$) and the unique parity $g_{9/2}$...

We outline the ab initio no core shell model and present recent results. Nuclear properties are evaluated with two‐nucleon (NN) and three‐nucleon interactions (TNI) derived within effective field theory (EFT) based on chiral perturbation theory (ChPT). Fitting two available parameters of the TNI generates good descriptions of light nuclei. In ano...

Recent developments in nuclear theory allow us to make a connection between quantum chromodynamics (QCD) and low-energy nuclear physics. First, chiral effective field theory (chiEFT) provides a natural hierarchy to define two-nucleon (NN), three-nucleon (NNN), and even four-nucleon interactions. Second, ab initio methods have been developed capable...

Properties of finite nuclei are evaluated with two-nucleon (NN) and three-nucleon (NNN) interactions derived within chiral effective field theory. The nuclear Hamiltonian is fixed by properties of the A=2 system, except for two low-energy constants (LECs) that parametrize the short range NNN interaction, which we constrain with the A=3 binding ener...

We study the spin-parity distribution P(J$^{\pi}$,E) of $^{156}$Gd excited states above the neutron separation energy that are expected to be populated via the neutron pickup reaction $^{157}$Gd($^{3}$He,$^{4}$He)$^{156}$Gd. In general, modeling of the spin-parity distribution is important for the applicability of the surrogate reaction technique a...

We propose a classical mechanism for the cosmic expansion during the radiation-dominated era. This mechanism assumes that the Universe is a two-component gas. The first component is a gas of ultra-relativistic “normal” particles described by an equation of state of an ideal quantum gas of massless particles. The second component consist of “unusual...

An indirect method for determining cross sections for reactions proceeding through a compound nucleus is presented. Exploring indirect approaches for obtaining reaction cross sections is important since a large number of reactions relevant to astrophysics cannot be measured with currently available techniques. Of particular importance are reactions...

Traditional realistic nucleon-nucleon (NN) interactions based on precision fits to 2-body data have not produced high-quality descriptions of light nuclei. Effective-Field theories (EFT) based on chiral-perturbation theory provide a natural scheme to derive inter-nucleon interactions and predict a three-nucleon interaction at next-to-next-to-leadin...

The complete exact solution of the T = 1 neutron-proton pairing Hamiltonian is presented in the context of the SO(5) Richardson-Gaudin model with nondegenerate single-particle levels and including isospin symmetry-breaking terms. The power of the method is illustrated with a numerical calculation for for 64Ge for a pf + g9/2 model space which is ou...

General structure of classical reparametrization-invariant matter systems, mainly the relativistic particle and its $d$-brane generalization, are studied. The exposition is in close analogy with the relativistic particle in an electromagnetic field as reparametrization-invariant system. The structure of a diffeomorphism invariant Lagrangian action...

The one-dimensional harmonic oscillator in a box problem is possibly the simplest example of a two-mode system. This system has two exactly solvable limits, the harmonic oscillator and a particle in a (one-dimensional) box. Each of the two limits has a characteristic spectral structure describing the two different excitation modes of the system. Ne...

Indirect methods play an important role in the determination of nuclear reaction cross sections. Often the cross section needed for a particular application cannot be measured directly since the relevant energy region is inaccessible or the target is too short-lived. This is particularly true for many reactions of interest to astrophysics. An innov...

Modern high-precision nucleon-nucleon (NN) interactions adjusted to reproduce the phase shifts in the two nucleon system need to be augmented by three-nucleon interactions (TNI) in order to reproduce properties of multi nucleon systems. Chiral perturbation theory (chiPT) at next-to-next-to-leading order (N^2LO) predicts three types of TNI terms. A...

Relative binding energies (RBEs) within three isotopic chains ($^{100-130}$Sn, $^{152-181}$Yb, and $^{181-202 }$Pb) have been studied using the exactly solvable extended pairing model (EPM) \cite{FPan04}. The unique pairing strength $G$, which reproduces the experimental RBEs, has been determined. Within EPM, $\log(G)$ is a smooth function of the m...

An indirect method for determining cross sections of reactions proceeding through a compound nucleus is presented. Some applications of the Surrogate nuclear reaction approach are considered and challenges that need to be addressed are outlined.

The mean-field plus extended pairing model proposed by the authors for describing well-deformed nuclei (F. Pan, V.G. Gueorguiev, J.P. Draayer, Phys. Rev. Lett. 92, 112503 (2004)) is revisited. Eigenvalues of the model can be determined by solving a single transidental equation. Results to date show that even through the model includes many-body int...

A mean-field Hamiltonian with an extended pairing interaction that includes multi-pair excitations is proposed for describing strongly-deformed nuclei. Solutions are easily obtained. The results show that even though the theory includes many-body interaction terms, the one- and two-body parts continue to dominate the dynamics for small values of th...

A mixed-symmetry nuclear shell-model scheme for carrying out calculations in regimes where there is a competition between two or more modes is proposed. A one-dimensional toy model is used to demonstrate the concept. The theory is then applied to $^{24}Mg$ and $^{44}Ti$. For lower pf-shell nuclei such as $^{44-48}Ti$ and $^{48}Cr$ there is strong S...

A Nilsson mean-field plus extended pairing interaction Hamiltonian with many-pair interaction terms is summarized. The investigation shows that one- and two-body interactions continue to dominate the dynamics for relatively small values of the pairing strength. As the strength of the pairing interaction grows, however, higher many-body interaction...

A mean-field plus extended pairing interaction Hamiltonian that includes multi-pair scattering terms is proposed for describing well-deformed nuclei. Eigenvalues of the model are easily obtained. The investigation shows that even through the extended pairing includes many-body terms, the one- and two-body interactions continue to dominate the dynam...

Shell-model calculations for 58Cu and 64Ge in the pf5/2g9/2 model space using a realistic interaction are reported and compared to those generated using an appropriately renormalized counterpart of the interaction in the truncated pf5/2 subspace. The results suggest that reliable computations can be performed in a space that does not explicitly inc...

The exact solvability of several nuclear models with non-degenerate single-particle energies is outlined and leads to a generalization of integrable Richardson-Gaudin models, like the $su(2)$-based fermion pairing, to any simple Lie algebra. As an example, the $so(5)\sim sp(4)$ model of T=1 pairing is discussed and illustrated for the case of $^{64...

Some results for two distinct but complementary exactly solvable algebraic models for pairing in atomic nuclei are presented: 1) binding energy predictions for isotopic chains of nuclei based on an extended pairing model that includes multi-pair excitations; and 2) fine structure effects among excited 0+ states in N ≈ Z nuclei that track with th...

We study binding energies in three isotopic chains ($^{100-130}$Sn, $^{152-181}$Yb, and $^{181-202}$Pb) using the extended pairing model with Nilsson single-particle energies. The exactly solvable nature of the model means that the pairing strength G(A) required to reproduce the experimental binding energies can be determined uniquely. The valence...

A one-dimensional harmonic oscillator in a box is used to introduce the oblique-basis concept. The method is extended to the nuclear shell model by combining traditional spherical shell model states, which yield a diagonal representation of the usual single-particle interaction, with SU(3) shell model collective configurations that track deformatio...

A specific q-deformation of the compact symplectic sp(4) algebra, one that is suitable for nuclear physics applications, is realized in terms of q-deformed fermion creation and annihilation operators of the shell-model. The generators of the algebra close on four distinct realizations of the uq(2) subalgebra. These reductions, which correspond to d...

A Nilsson mean-field plus extended pairing interaction Hamiltonian with many-pair interaction terms is proposed. Eigenvalues of the extended pairing model are easy to obtain. Our investigation shows that one- and two-body interactions continue to dominate the dynamics for relatively small values of the pairing strength. As the strength of the pairi...

The spectrum and wave functions of 44Ti are studied in oblique-basis calculations using spherical and SU(3) shell-model states. Although the results for 44Ti are not as good as those previously reported for 24Mg, due primarily to the strong spinorbit interaction that generates significant splitting of the single-particle energies that breaks the SU...

We discuss the extension of the Richardson-Gaudin models along two lines. We #rst describe a new family of exactly solvable atom-molecule Hamiltonians obtained by coupling a bosonic mode to the rational family. We then present the generalization of the Richardson-Gaudin models to any simple Lie algebra. As an example of relevance to nuclear structu...

Determining reaction cross sections for unstable nuclei is a major challenge for nuclear physics and astrophysics. The Surrogate Nuclear Reaction technique allows one to indirectly determine the cross section for a two-step reaction a + A arrow B arrow c + C proceeding through a compound state B^*: B^* is produced via an alternative (``Surrogate'')...

A mixed-symmetry nuclear shell-model scheme for carrying out calculations in regimes where there is a competition between two or more modes is proposed. A one-dimensional toy model is used to demonstrate the concept. The theory is then applied to $^{24}Mg$ and $^{44}Ti$. For lower pf-shell nuclei such as $^{44-48}Ti$ and $^{48}Cr$ there is strong S...

The structure of a diffeomorphism invariant Lagrangians for an extended object W embedded in a bulk space M is discussed by following a close analogy with the relativistic particle in electromagnetic field as a system that is reparametrization-invariant. The current construction naturally contains, relativistic point particle, string theory, and Di...

The properties of atomic nuclei far from the line of stability is of major current interest in nuclear physics. A factor limiting reliable theoretical calculations in such domains is the size of the valence model space that is required for realistic calculations. This same challenge arises for upper pf-shell nuclei. Using symmetries of the system,...