A5028391299- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Relativity and Gravitational Theory
- Dark Matter and Cosmic Phenomena
- Particle physics theoretical and experimental studies
- Noncommutative and Quantum Gravity Theories
- Galaxies: Formation, Evolution, Phenomena
- Geophysics and Gravity Measurements
- Earth Systems and Cosmic Evolution
- Solar and Space Plasma Dynamics
- Quantum Chromodynamics and Particle Interactions
- Advanced Differential Geometry Research
- Computational Physics and Python Applications
- Quantum Mechanics and Applications
- Pulsars and Gravitational Waves Research
- Quantum Electrodynamics and Casimir Effect
- Advanced Mathematical Theories and Applications
- Astrophysics and Cosmic Phenomena
- Advanced Thermodynamics and Statistical Mechanics
- Scientific Research and Discoveries
- Quantum and Classical Electrodynamics
- Algebraic and Geometric Analysis
- Quantum, superfluid, helium dynamics
- Advanced Topics in Algebra
- Astrophysical Phenomena and Observations
Ben-Gurion University of the Negev
2016-2025
Frankfurt Institute for Advanced Studies
2017-2025
College of The Bahamas
2018-2024
University of Regensburg
2023
University of Lisbon
2022
Institute for Fundamental Physics of the Universe
2022
Instituto Politécnico de Lisboa
2022
Institute for Nuclear Research and Nuclear Energy
2010-2016
DTU Space
2016
Bulgarian Academy of Sciences
2010-2016
The possibility of localized inflation is investigated by calculating the dynamics a spherically symmetric region false vacuum which separated domain wall from an infinite true vacuum. For range initial conditions, false-vacuum will undergo inflation. An observer in exterior true-vacuum describe system as black hole, while interior closed universe completely disconnects original spacetime. We suggest that this mechanism likely to lead instability Minkowski space: space might quantum...
The exploration of the universe has recently entered a new era thanks to multi-messenger paradigm, characterized by continuous increase in quantity and quality experimental data that is obtained detection various cosmic messengers (photons, neutrinos, rays gravitational waves) from numerous origins. They give us information about their sources properties intergalactic medium. Moreover, astronomy opens up possibility search for phenomenological signatures quantum gravity. On one hand, most...
The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO look for axions or axion-like particles (ALPs) originating in the Sun via Primakoff conversion of solar plasma photons. In terms signal-to-noise ratio, about 4–5 orders magnitude more sensitive than CAST, currently most powerful helioscope, reaching sensitivity to axion-photon couplings down few × 10−12 GeV−1 and thus probing large fraction unexplored ALP parameter space....
Abstract The unification of quantum mechanics and general relativity has long been elusive. Only recently have empirical predictions various possible theories gravity put to test, where a clear signal properties is still missing. dawn multi-messenger high-energy astrophysics tremendously beneficial, as it allows us study particles with much higher energies travelling longer distances than in terrestrial experiments, but more progress needed on several fronts. A thorough appraisal current...
We consider a modified gravity plus single scalar-field model, where the scalar Lagrangian couples symmetrically both to standard Riemannian volume-form (spacetime integration measure density) given by square root of determinant metric, as well another non-Riemannian in terms an auxiliary maximal-rank antisymmetric tensor gauge field. As shown previous paper, pertinent dynamics provides exact unified description dark energy via dynamical generation cosmological constant, and matter "dust"...
In this paper we consider a new approach to unify inflation and the late universe with dark energy matter formulated in model that includes non-Riemannian metric independent measure scalar field spontaneously broken scale symmetry. Here first of all is possible, which then followed by reheating oscillating period leads formation kind particles, including fermions, as expands can contribute universe. During inflationary epoch, find different constraints on parameter space associated effective...
Realizations of scale invariance are studied in the context a gravitational theory where action (in first order formalism) is form $S = \int L_{1} \Phi d^{4}x$ + $\int L_{2}\sqrt{-g}d^{4}x$ $\Phi$ density built out degrees freedom, "measure fields" independent $g_{\mu\nu}$ and matter fields appearing $L_{1}$, $L_{2}$. If $L_{1}$ contains curvature, scalar potential $V(\phi)$ kinetic term for $\phi$, $L_{2}$ another $U(\phi)$, then true vacuum state has zero energy density, when analyzed...
Summary of abstract Field theory models including gauge theories with SSB are presented where the energy density true vacuum state (TVS) is zero without fine tuning. The above constructed in gravitational a measure integration \Phi action not necessarily \sqrt{-g} but it determined dynamically through additional degrees freedom. ratio \Phi/\sqrt{-g} scalar field which can be solved terms matter freedom due to existence constraint. We study few explicit possible combine solution cosmological...
This article investigates the modified Raychaudhuri Equation (RE) in context of Non-Gravitating Vacuum Energy (NGVE) theory and its implications for various cosmological characteristics. The equation is formulated based on NGVE framework, which global scale invariance generates a unique geometry. newly developed geometry introduces metric that conformally connected to conventional metric, with conformal factor dependent scalar field potentials. study carried out under framework flat...
Abstract The string and brane tensions do not have to be put in by hand, they can dynamically generated, as the case when we formulate theories modified measure formalism. Then appears, but an additional dynamical degree of freedom. It seen however that these or are universal, rather each generates its own tension, which a different value for brane. consequences this spectrum is profound both ultraviolet behavior low energy physics. There should also considerable effect effective gravity...
For Einstein's General Relativity (GR) or the alternatives suggested up to date vacuum energy gravitates. We present a model where new measure is introduced for integration of total action in D-dimensional space-time. This built from D scalar fields $φ_{a}$. As consequence such choice measure, matter lagrangian $L_{m}$ can be changed by adding constant while no gravitational effects, like cosmological term, are induced. Such Non-Gravitating Vacuum Energy (NGVE) theory has an infinite...
Here we generalize ideas of unified dark matter–dark energy in the context two measure theories and dynamical space time theories. In one uses metric independent volume elements this allows to construct energy, where cosmological constant appears as an integration associated with equation motion fields. The space-time by introducing a vector field whose guarantees conservation certain Energy Momentum tensor, which may be related, but general is not same gravitational tensor. We propose...
A unification of dark matter and energy based on a dynamical spacetime theory is suggested. By introducing vector field ${\ensuremath{\chi}}_{\ensuremath{\mu}}$ as Lagrange multiplier, conservation an momentum tensor ${T}_{(\ensuremath{\chi})}^{\ensuremath{\mu}\ensuremath{\nu}}$ implemented. This Lagrangian generalizes the ``unified from scalar different quintessence'' [Phys. Rev. D 81, 043520 (2010)], which did not consider formulation. generalization allows solutions were found previously,...
We show that dark energy and matter can be described simultaneously by ordinary Einstein gravity interacting with a single scalar field provided the Lagrangian couples in symmetric fashion to two different spacetime volume forms (covariant integration measure densities) on manifold – one standard Riemannian given $$\sqrt{-g}$$ (square root of determinant pertinent metric) another non-Riemannian form independent metric, defined terms an auxiliary antisymmetric tensor gauge maximal rank....
Generalized ideas of unified dark matter and energy in the context dynamical space time theories with a diffusive transfer are studied. The space-time introduce vector field whose equation motion guarantees conservation certain momentum tensor, which may be related, but general is not same as gravitational tensor. This particular tensor built from combination scalar fields derivatives kinetic terms, possibly potentials for field. By demanding that gradient theory becomes interacting matter....
Abstract An extension to the Einstein–Cartan (EC) action is discussed in terms of cosmological solutions. The torsion incorporated EC Lagrangian assumed be totally anti-symmetric, represented by a time-like axial vector $$S^\mu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mi>S</mml:mi> <mml:mi>μ</mml:mi> </mml:msup> </mml:math> . dynamics invoked novel kinetic term. Here we show that this term gives rise dark energy, while quadratic term, emanating from part,...
The unification of quantum mechanics and general relativity has long been elusive. Only recently have empirical predictions various possible theories gravity put to test. dawn multi-messenger high-energy astrophysics tremendously beneficial, as it allows us study particles with much higher energies travelling longer distances than in terrestrial experiments, but more progress is needed on several fronts. A thorough appraisal current strategies experimental frameworks, regarding...
We consider the effects of adding a scale invariant $R^{2}$ term to action model (SIM) studied previously by one us (E.I.G., Mod. Phys. Lett. A14, 1043 (1999)). The SIM belongs general class theories, where an integration measure independent metric is introduced. To implement invariance (S.I.), dilaton field equations motion associated with new gives rise spontaneous symmetry breaking (S.S.B) S.I.. After S.S.B. S.I. in term, it found that non trivial potential for generated. This contains...
The gravitational field produced by a spherically symmetric "hedgehog" configuration in scalar theories with global SO(3) symmetry (or higher) is studied the limit which these models become nonlinear $\ensuremath{\sigma}$ models. same effect can be generated set of cosmic strings intersecting at point, that one considers continuous distribution such (to referred to as "string hedgehog"). When energy densities associated hedgehog are small, we obtain static geometry, but for higher values,...
In this work we construct a unified model of dark energy and matter. This is done with the following three elements: gravitating scalar field, ϕ non-conventional kinetic term, as in string theory tachyon; an arbitrary potential, V(ϕ); two measures — metric measure ((−g)1/2) non-metric (Φ). The has interesting features: (i) For potentials which are unstable would give rise to tachyonic can stabilize field. (ii) form matter that results from fairly insensitive exact field potential.
The use in the action integral of totally divergent densities generally coordinate invariant theories can lead to interesting mechanisms spontaneous symmetry breaking scale invariance. With dependence on a metric independent density $\Phi$, $4D$ , we define $\Phi =\varepsilon^{\mu\nu\alpha\beta}\partial_{\mu}A_{\nu\alpha\beta}$ that gives new mechanism for 4-D gravity plus matter fields, through $A_{\nu\alpha\beta}$ equations motion which an integration constant breaks symmetry, while...
A recently proposed Dynamical Space-time Cosmology (DSC) that unifies dark energy and matter is studied. The general action of this scenario includes a Lagrange multiplier, which coupled to the momentum tensor scalar field different from quintessence. First for various types potentials we implement critical point analysis find solutions lead cosmic acceleration under certain conditions stable late-time attractors. Then DSC cosmology confronted with latest cosmological data low-redshift...