A5019460584- Black Holes and Theoretical Physics
- Cosmology and Gravitation Theories
- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- Galaxies: Formation, Evolution, Phenomena
- Neutrino Physics Research
- Noncommutative and Quantum Gravity Theories
- Astrophysics and Cosmic Phenomena
- Dark Matter and Cosmic Phenomena
- Advanced Thermodynamics and Statistical Mechanics
- Relativity and Gravitational Theory
- Quantum Mechanics and Applications
- Quantum chaos and dynamical systems
- Advanced Differential Geometry Research
- Quantum Electrodynamics and Casimir Effect
- High-Energy Particle Collisions Research
- Particle Detector Development and Performance
- Nonlinear Waves and Solitons
- Political Economy and Marxism
- Theoretical and Computational Physics
- Spectral Theory in Mathematical Physics
- Nonlinear Photonic Systems
- Quantum, superfluid, helium dynamics
- Earth Systems and Cosmic Evolution
- High-pressure geophysics and materials
Institute for Nuclear Research
2010-2024
Moscow Institute of Physics and Technology
2014-2024
Chinese University of Hong Kong
2012
Institute of Theoretical Physics
2012
Lomonosov Moscow State University
1996-2011
Russian Academy of Sciences
2004-2009
Université Libre de Bruxelles
2000-2005
We study spatially flat bouncing cosmologies and models with the early-time Genesis epoch in a popular class of generalized Galileon theories. ask whether there exist solutions these types which are free gradient ghost instabilities. find that irrespectively forms Lagrangian functions, either plagued instabilities or have singularities. The same result holds for original model its variants scale factor tends to constant as t → −∞. remains valid theories additional matter obeys Null Energy...
Photons may convert to axion-like particles (ALPs) in external magnetic fields. Under certain conditions, this effect should result irregular features observed spectra of astrophysical sources. Lack such irregularities particular was used constrain ALP parameters, with two most popular sources being the radio galaxy NGC 1275 and blazar PKS 2155–304. The and, consequently, constraints, depend on fields through which light from source is propagated. Here, we revisit constraints gamma-ray...
It is argued that the amplitudes of production n soft scalar particles by one or a few energetic ones in theories such as \ensuremath{\lambda}${\mathit{cphi}}^{4}$ have exponential form ${\mathit{A}}_{\mathit{n}}$\ensuremath{\propto} \ensuremath{\surd}n! exp[1/\ensuremath{\lambda}F(\ensuremath{\lambda}n,\ensuremath{\epsilon})], regime \ensuremath{\lambda}\ensuremath{\rightarrow}0, \ensuremath{\lambda}n=fixed, \ensuremath{\epsilon}=fixed, where \ensuremath{\epsilon} typical kinetic energy...
We discuss the physics case for and concept of a medium-scale axion helioscope with sensitivities in axion-photon coupling few times better than CERN Axion Solar Telescope (CAST). Search an axion-like particle these couplings is motivated by several persistent astrophysical anomalies. present early conceptual design, existing infrastructure, projected sensitivity timeline such (Troitsk Experiment, TASTE) to be constructed Institute Nuclear Research, Troitsk, Russia. The proposed instrument...
Phantom fields with negative kinetic energy are often plagued by vacuum quantum instability in the ultraviolet region. We present a Lorentz-violating dark model free from this problem and show that crossing of cosmological constant boundary w = −1 to phantom equation state is realized before reaching de Sitter attractor. Another interesting feature peculiar time dependence effective Newton's constant; magnitude effect naturally small but may be close experimental limits. also derive momentum...
We consider a scenario in which primordial scalar perturbations are generated when complex conformal field rolls down its negative quartic potential. Initially, these the of phase this field; they converted into adiabatic at later stage. A potentially dangerous feature is existence radial direction, have red power spectrum. show, however, that to linear order small parameter - self-coupling infrared effects completely harmless, as can be absorbed redefinition. then evaluate statistical...
We consider theories which explain the flatness of power spectrum scalar perturbations in Universe by conformal invariance, such as rolling model and Galilean Genesis. show that to leading {\it non-linear} order, all models from this class behave one same way, at least if energy density relevant fields is small compared total (spectator approximation). then turn intrinsic non-Gaussianities these (as opposed may be generated during subsequent evolution). The bispectrum vanishes, so we perform...
Scalar cosmological perturbations with nearly flat power spectrum may originate from of the phase a scalar field conformally coupled to gravity and rolling down negative quartic potential. We consider version this scenario whose specific property is long intermediate stage between end conformal horizon exit perturbations. Such natural, e.g., in cosmologies ekpyrosis or genesis. Its existence results small tilt, statistical anisotropy all even multipoles starting quardupole general structure...
We investigate five-dimensional braneworld setups with broken Lorentz invariance continuing the developments of [P. Koroteev and M. Libanov, J. High Energy Phys. 02 (2008) 104], where a family static self-tuning solutions was found. show that several known models can be embedded into this family. Then we give qualitative analysis spectra field fluctuations in backgrounds invariance. also elaborate on one particular model study scalar spinor fields it. It turns out have found possess very...
Primordial scalar perturbations may be generated when complex conformal field rolls down its negative quartic potential. We begin with the discussion of peculiar infrared properties this scenario. then consider statistical anisotropy inherent in model. Finally, we discuss non-Gaussianity perturbations. Because symmetries, bispectrum vanishes identically. present a general expression for trispectrum and give explicit form folded limit.
It has been shown recently that the amplitude of creation n real scalar particles by one virtual boson near n-particle threshold exhibits exponential behavior at n\ensuremath{\sim}1/\ensuremath{\lambda}. We extend this result to processes multiparticle production two bosons. find both tree-level and leading-n-loop corrections have same behavior, with common exponent for 1\ensuremath{\rightarrow}n 2\ensuremath{\rightarrow}n processes, various kinematics. This strongly indicates amplitudes is...
We consider an inflating brane-world setup in which 4-dimensional Lorentz-invariance is violated at high 3-momentum scale $P_{LV} \gg H$, where $H$ the inflationary Hubble parameter. study massless scalar field this background as a model for cosmological perturbations. Towards end of inflation, spectrum has both standard, part due to brane-localized mode, and exotic, bulk induced contribution. The suppression latter power-law only, $(H/P_{LV})^\alpha$, provided that there exist modes with...