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Sep 18, 2013
09/13

by
I. I. Tkachev

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Symmetry restoration processes during the non-equilibrium stage of ``preheating'' after inflation is studied. It is shown that symmetry restoration is very efficient when the majority of created particles are concentrated at energies much smaller than the temperature $T$ in equilibrium. The strength of symmetry restoration measured in terms of the equivalent temperature can exceed $T$ by many orders of magnitude. In some models the effect can be equivalent to that if the temperature of instant...

Source: http://arxiv.org/abs/hep-th/9510146v3

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Jun 30, 2018
06/18

by
Igor I. Tkachev

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Non-linear effects in the evolution of the axion field in the early Universe may lead to the formation of gravitationally bound clumps of axions, known as "miniclusters". Minicluster masses should be in the range $M_{\rm mc}\sim10^{-12} M_\odot$, and in plausible early-Universe scenarios a significant fraction of the mass density of the Universe may be in the form of axion miniclusters. Here I argue that observed properties (total energy release, duration, high brightness temperature,...

Topics: High Energy Astrophysical Phenomena, Astrophysics

Source: http://arxiv.org/abs/1411.3900

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Sep 18, 2013
09/13

by
I. I. Tkachev

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Two processes of matter creation after inflation: 1) gravitational creation of superheavy (quasi)stable particles, and 2) non-thermal phase transitions leading to formation of topological defects, may be relevant to the resolution of the puzzle of cosmic rays observed with energies beyond GZK cut-off. Both possibilities are reviewed in this talk.

Source: http://arxiv.org/abs/hep-ph/9901428v1

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Sep 20, 2013
09/13

by
I. I. Tkachev

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In this astro-particle lecture course I shall try to emphasize evidence of the new physics which we have in cosmological and astrophysical data. This includes support of the inflationary model, necessity of dark energy and of non-baryonic dark matter, the Grizen-Zatsepin-Kuzmin puzzle of the ultra-high energy cosmic rays.

Source: http://arxiv.org/abs/hep-ph/0405168v1

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Sep 20, 2013
09/13

by
P. Tinyakov; I. Tkachev

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In a series of papers we have found statistically significant correlations between arrival directions of ultra-high energy cosmic rays and BL Lacertae objects. Recently, our calculations were partly repeated by Evans, Ferrer and Sarkar with different conclusions. We demonstrate that the criticism of Evans, Ferrer and Sarkar is incorrect. We also present the details of our method.

Source: http://arxiv.org/abs/astro-ph/0301336v2

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Sep 17, 2013
09/13

by
P. Tinyakov; I. Tkachev

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We develop a formalism which allows to study correlations of charged UHECR with potential sources without using any Galactic Magnetic Field (GMF) model. The method is free of subjective chose of parameters on which the significance of correlations depends strongly. We show that correlations of the AGASA dataset with BL Lacs (found previously after reconstruction of particle trajectories in a specific GMF) are present intrinsically and can be detected without reference to a particular model of...

Source: http://arxiv.org/abs/astro-ph/0305363v1

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Sep 20, 2013
09/13

by
R. Micha; I. Tkachev

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After a short review of inlationary preheating, we discuss the development of equilibrium in the frameworks of massless $\lambda \Phi^4$ model. It is shown that the process is characterised by the appearance of Kolmogorov spectra and the evolution towards thermal equilibrium follows self-similar dynamics. Simplified kinetic theory gives values for all characteristic exponents which are close to what is observed in lattice simulations. This allows estimation of the resulting reheating...

Source: http://arxiv.org/abs/hep-ph/0301249v1

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Sep 18, 2013
09/13

by
P. Tinyakov; I. Tkachev

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We analyze the existing evidence that BL Lacertae objects (BL Lacs) are sources of the highest-energy cosmic rays. We argue that three independent signatures observed in the real data -- (1) improvement of correlations with corrections of trajectories for the Galactic magnetic field; (2) connection between gamma-ray and UHECR emissions; (3) non-uniform distribution of correlating rays over the sky -- are consistent with the hypothesis that a substantial fraction of cosmic rays in the energy...

Source: http://arxiv.org/abs/hep-ph/0212223v1

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Jul 20, 2013
07/13

by
S. Khlebnikov; I. Tkachev

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We consider phase separation in nonequilibrium Bose gas with an attractive interaction between the particles. Using numerical integrations on a lattice, we show that the system evolves into a state that contains drops of Bose-Einstein condensate suspended in uncondensed gas. When the initial gas is sufficiently rarefied, the rate of formation of this quantum dew scales with the initial density as expected for a process governed by two-particle collisions.

Source: http://arxiv.org/abs/hep-ph/9902272v1

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Sep 18, 2013
09/13

by
G. Steigman; I. Tkachev

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We obtain restrictions on the universal baryon fraction, f_B = Omega_B/Omega_0, by assuming that the observed microlensing events towards the Large Magellanic Cloud are due to baryonic MACHOs in the halo of the Galaxy and by extracting a bound to the total mass of the Milky Way from the motion of tracer galaxies in the Local Group. We find a lower bound f_B > 0.29^{+0.18}_{-0.15}. Consistency with the predictions of primordial nucleosynthesis leads to the further constraint on the total mass...

Source: http://arxiv.org/abs/astro-ph/9803008v2

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Sep 22, 2013
09/13

by
D. Semikoz; I. Tkachev

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The process of condensation in the system of scalar Bosons with weak $\lambda \phi^4$ interaction is considered. Boltzmann kinetic equation is solved numerically. Bose condensation proceeds in two stages: At the first stage condensate is still absent but there is non-zero inflow of particles towards $\vec{{\bf p}} = 0$ and the distribution function at $\vec{{\bf p}} = 0$ grows from finite values to infinity. At the second stage there are two components, condensate and particles, reaching their...

Source: http://arxiv.org/abs/hep-ph/9409202v1

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Sep 18, 2013
09/13

by
A. Riotto; I. I. Tkachev

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We calculate the strength of symmetry restoration effects in highly non-equilibrium states which can arise, for example, during preheating after inflation. We show that in certain parameter range the one-loop results are unstable, requiring summation of multiloop diagrams. We solve this problem for the $O(N)$ model in the large $N$-limit and show that the symmetry restoration may be less effective than what predicted by the one-loop estimate.

Source: http://arxiv.org/abs/hep-ph/9604444v1

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Sep 22, 2013
09/13

by
Raphael Micha; Igor I. Tkachev

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We study, analytically and with lattice simulations, the decay of coherent field oscillations and the subsequent thermalization of the resulting stochastic classical wave-field. The problem of reheating of the Universe after inflation constitutes our prime motivation and application of the results. We identify three different stages of these processes. During the initial stage of ``parametric resonance'', only a small fraction of the initial inflaton energy is transferred to fluctuations in the...

Source: http://arxiv.org/abs/hep-ph/0403101v1

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Sep 18, 2013
09/13

by
R. Micha; I. I. Tkachev

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We study, both numerically and analytically, the development of equilibrium after preheating. We show that the process is characterised by the appearance of Kolmogorov spectra and the evolution towards thermal equilibrium follows self-similar dynamics. Simplified kinetic theory gives values for all characteristic exponents which are close to what is observed in lattice simulations. The resulting time for thermalization is long, and temperature at thermalization is low, $T \sim 100$ eV in the...

Source: http://arxiv.org/abs/hep-ph/0210202v1

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Sep 18, 2013
09/13

by
V. A. Kuzmin; I. I. Tkachev

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Cosmic rays of the highest energy, above the Greisen-Zatsepin-Kuzmin cut-off of the spectrum, may originate in decays of superheavy long-living X-particles. These particles may be produced in the early Universe from vacuum fluctuations during or after inflation and may constitute a considerable fraction of Cold Dark Matter. We calculate numerically their abundance for a wide range of models. X-particles are considered to be either bosons or fermions. Particles that are several times heavier...

Source: http://arxiv.org/abs/hep-ph/9809547v1

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Sep 21, 2013
09/13

by
Edward W. Kolb; Igor I. Tkachev

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The $(3+1)$-dimensional evolution of an inhomogeneous axion field configuration around the QCD epoch is studied numerically, including important non-linear effects due to the attractive self-interaction. It is found that axion perturbations on scales corresponding to causally disconnected regions at $T \sim 1 \, {\rm GeV}$ can lead to very dense pseudo-soliton configurations we call axitons. These configurations evolve to axion miniclusters with present density $\rho_a \ga 10^{-8}\,{\rm g \,...

Source: http://arxiv.org/abs/astro-ph/9311037v1

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Sep 23, 2013
09/13

by
P. G. Tinyakov; I. I. Tkachev

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We express the mean square deflections of the ultra-high energy cosmic rays (UHECR) caused by the random component of the Galactic magnetic field (GMF) in terms of the GMF power spectrum. We use recent measurements of the GMF spectra in several sky patches to estimate the deflections quantitatively. We find that deflections due to the random field constitute $0.03-0.3$ of the deflections which are due to the regular component and depend on the direction on the sky. They are small enough not to...

Source: http://arxiv.org/abs/astro-ph/0411669v2

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Jun 29, 2018
06/18

by
A. Chudaykin; D. Gorbunov; I. Tkachev

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It has been recently suggested~\cite{Berezhiani:2015yta} that emerging tension between cosmological parameter values derived in high-redshift (CMB anisotropy) and low-redshift (cluster counts, Hubble constant) measurements can be reconciled in a model which contains subdominant fraction of dark matter decaying after recombination. We check the model against the CMB Planck data. We find that lensing of the CMB anisotropies by the large-scale structure gives strong extra constraints on this...

Topics: Astrophysics, High Energy Physics - Phenomenology, Cosmology and Nongalactic Astrophysics

Source: http://arxiv.org/abs/1602.08121

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3.0

Jun 30, 2018
06/18

by
A. Dolgov; V. Halenka; I. Tkachev

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We revise observational constraints on the class of models of modified gravity which at low redshifts lead to a power-law cosmology. To this end we use available public data on Supernova Ia and on baryon acoustic oscillations. We show that the expansion regime $a(t) \sim t^{\beta}$ with $\beta$ close to 3/2 a spatially flat universe is a good fit to these data.

Topics: Astrophysics, Cosmology and Nongalactic Astrophysics

Source: http://arxiv.org/abs/1406.2445

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37

Sep 22, 2013
09/13

by
P. G. Tinyakov; I. I. Tkachev

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We reconstruct the trajectories of ultra-high energy cosmic rays (UHECR) - observed by the AGASA experiment - in the Galactic magnetic field assuming that all particles have the same charge. We then study correlations between the reconstructed events and BL Lacs. The correlations have significance below 10^{-3} in the case of particles with charge +1. In the case of charge -1 the correlations are absent. We interpret this as evidence that protons are present in the flux of UHECR. Observed...

Source: http://arxiv.org/abs/astro-ph/0111305v1

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63

Sep 20, 2013
09/13

by
V. A. Kuzmin; I. I. Tkachev

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The highest energy cosmic rays, above the Greisen-Zatsepin-Kuzmin cut-off of cosmic ray spectrum, may be produced in decays of superheavy long-living X-particles. We conjecture that these particles may be produced naturally in the early Universe from vacuum fluctuations during inflation and may constitute a considerable fraction of Cold Dark Matter. We predict a new cut-off in the UHE cosmic ray spectrum E_{cut-off} < m_inflaton \approx 10^{13} GeV, the exact position of the cut-off and the...

Source: http://arxiv.org/abs/hep-ph/9802304v1

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51

Sep 23, 2013
09/13

by
A. Boyarsky; A. Neronov; I. Tkachev

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We canonically quantize the dynamics of the brane universe embedded into the five-dimensional Schwarzschild-anti-deSitter bulk space-time. We show that in the brane-world settings the formulation of the quantum cosmology, including the problem of initial conditions, is conceptually more simple than in the 3+1-dimensional case. The Wheeler-deWitt equation is a finite-difference equation. It is exactly solvable in the case of a flat universe and we find the ground state of the system. The closed...

Source: http://arxiv.org/abs/gr-qc/0411144v1

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Sep 18, 2013
09/13

by
S. Dubovsky; P. Tinyakov; I. Tkachev

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We study Lorentz-violating models of massive gravity which preserve rotations and are invariant under time-dependent shifts of the spatial coordinates. In the linear approximation the Newtonian potential in these models has an extra ``confining'' term proportional to the distance from the source. We argue that during cosmological expansion the Universe may be driven to an attractor point with larger symmetry which includes particular simultaneous dilatations of time and space coordinates. The...

Source: http://arxiv.org/abs/hep-th/0504067v1

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Sep 23, 2013
09/13

by
S. Yu. Khlebnikov; I. I. Tkachev

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We study numerically the decay of massive and massless inflatons into massive excitations, via a $\phi^2 X^2$ coupling, in the expanding Universe. We find that a wide enough resonance can survive the Universe expansion, though account for the expansion is very important for determining precisely how wide it should be. For a massive inflaton, the effective production of particles with mass ten times that of the inflaton requires very large values of the resonance parameter $q$, $q\gsim 10^8$....

Source: http://arxiv.org/abs/hep-ph/9608458v1

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Sep 20, 2013
09/13

by
P. G. Tinyakov; I. I. Tkachev

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The recently observed correlation between HiRes stereo cosmic ray events with energies E ~ 10 EeV and BL Lacs occurs at an angle which strongly suggests that the primary particles are neutral. We analyze whether this correlation, if not a statistical fluctuation, can be explained within the Standard Model, i.e., assuming only known particles and interactions. We have not found a plausible process which can account for these correlations. The mechanism which comes closest -- the conversion of...

Source: http://arxiv.org/abs/astro-ph/0612359v1

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Sep 17, 2013
09/13

by
A. A. Starobinsky; I. I. Tkachev

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We consider observational constraints on creation of particles induced by hypothetical trans-Planckian effects during the current stage of the Universe expansion. We show that compatibility with the diffuse gamma-ray background measured by the EGRET experiment strongly restricts this creation. In particular, it rules out the possibility to detect signatures of such short distance effects in anisotropies of the cosmic microwave background radiation. On the other hand, a possibility that some...

Source: http://arxiv.org/abs/astro-ph/0207572v2

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47

Sep 20, 2013
09/13

by
S. Yu. Khlebnikov; I. I. Tkachev

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We present results of fully non-linear calculations of decay of the inflaton interacting with another scalar field X. Combining numerical results for cosmologically interesting range of resonance parameter, q \leq 10^6, with analytical estimates, we extrapolate them to larger q. We find that scattering of X fluctuations off the Bose condensate is a very efficient mechanism limiting growth of X fluctuations. For a single-component X, the resulting variance, at large q, is much smaller than that...

Source: http://arxiv.org/abs/hep-ph/9610477v3

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Sep 21, 2013
09/13

by
A. Neronov; D. Semikoz; I. Tkachev

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We develop a model of ultra-high energy cosmic ray (UHECR) production via acceleration in a rotation-induced electric field in vacuum gaps in the magnetospheres of supermassive black holes (BH). We show that if the poloidal magnetic field near the BH horizon is misaligned with the BH rotation axis, charged particles, which initially spiral into the BH hole along the equatorial plane, penetrate into the regions above the BH "polar caps" and are ejected with high energies to infinity....

Source: http://arxiv.org/abs/0712.1737v2

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Sep 19, 2013
09/13

by
Edward W. Kolb; Igor I. Tkachev

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Evolution of inhomogeneities in the axion field around the QCD epoch is studied numerically, including for the first time important non-linear effects. It is found that perturbations on scales corresponding to causally disconnected regions at $T \sim 1 \, {\rm GeV}$ can lead to very dense axion clumps, with present density $\rho_a \ga 10^{-8}\,{\rm g \, cm^{-3}}$. This is high enough for the collisional $2a \rightarrow 2a$ process to lead to Bose--Einstein relaxation in the gravitationally...

Source: http://arxiv.org/abs/hep-ph/9303313v1

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Sep 22, 2013
09/13

by
Mikhail E. Shaposhnikov; Igor I. Tkachev

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We propose a scheme leading to a non-perturbative definition of lattice field theories which are scale-invariant on the quantum level. A key idea of the construction is the replacement of the lattice spacing by a propagating dynamical field -- the dilaton. We describe how to select non-perturbatively the phenomenologically viable theories where the scale invariance is broken spontaneously. Relation to gravity is also discussed.

Source: http://arxiv.org/abs/0811.1967v1

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Sep 19, 2013
09/13

by
P. G. Tinyakov; I. I. Tkachev

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We calculate the angular two-point correlation function of ultra-high energy cosmic rays (UHECR) observed by AGASA and Yakutsk experiments. In both data sets, there is a strong signal at highest energies, which is concentrated in the first bin of the size of the angular resolution of the experiment. For the uniform distribution of sources, the probability of a chance clustering is 4 x 10^{-6}. Correlations are absent or not significant at larger angles. This favors the models with compact...

Source: http://arxiv.org/abs/astro-ph/0102101v2

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Sep 21, 2013
09/13

by
A. Neronov; P. Tinyakov; I. Tkachev

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We study numerically particle acceleration by the electric field induced near the horizon of a rotating supermassive (M \sim 10^9-10^{10} M_{\odot}) black hole embedded in the magnetic field B. We find that acceleration of protons to energy E > 10^{20} eV is possible only at extreme values of M and B. We also find that the acceleration is very inefficient and is accompanied by a broad band MeV-TeV radiation whose total power exceeds at least by a factor of 1000 the total power emitted in...

Source: http://arxiv.org/abs/astro-ph/0402132v2

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Sep 21, 2013
09/13

by
Edward W. Kolb; Igor I. Tkachev

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Large-amplitude isothermal fluctuations in the dark matter energy density, parameterized by $\Phi\equiv\delta\rhodm/\rhodm$, are studied within the framework of a spherical collapse model. For $\Phi \ga 1$, a fluctuation collapses in the radiation-dominated epoch and produces a dense dark-matter object. The final density of the virialized object is found to be $\rho_F \approx 140\, \Phi^3 (\Phi+1) \rhoeq$, where $\rhoeq$ is the matter density at equal matter and radiation energy density. This...

Source: http://arxiv.org/abs/astro-ph/9403011v1

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Sep 18, 2013
09/13

by
Vadim A. Kuzmin; Igor I. Tkachev

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There are two processes of matter creation after inflation that may be relevant to the resolution of the puzzle of cosmic rays observed with energies beyond GZK cut-off: 1) gravitational creation of superheavy (quasi)stable particles, and 2) non-thermal phase transitions leading to formation of topological defects. We review both possibilities.

Source: http://arxiv.org/abs/hep-ph/9903542v1

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Sep 20, 2013
09/13

by
S. Yu. Khlebnikov; I. I. Tkachev

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We present the first fully non-linear calculation of inflaton decay. We map inflaton decay onto an equivalent classical problem and solve the latter numerically. In the $\lambda\phi^4$ model, we find that parametric resonance develops slower and ends at smaller values of fluctuating fields, as compared to estimates existing in literature. We also observe a number of qualitatively new phenomena, including a stage of semiclassical thermalization, during which the decay of inflaton is essentially...

Source: http://arxiv.org/abs/hep-ph/9603378v2

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Sep 18, 2013
09/13

by
E. W. Kolb; I. I. Tkachev

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Non-linear effects in the evolution of the axion field in the early Universe may lead to the formation of gravitationally bound clumps of axions, known as ``miniclusters.'' Minicluster masses and radii should be in the range $M_{\rm mc}\sim10^{-12} M_\odot$ and $R_{\rm mc} \sim 10^{10}$cm, and in plausible early-Universe scenarios a significant fraction of the mass density of the Universe may be in the form of axion miniclusters. If such axion miniclusters exist, they would have the physical...

Source: http://arxiv.org/abs/astro-ph/9510043v1

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Sep 19, 2013
09/13

by
P. G. Tinyakov; I. I. Tkachev

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We calculate angular correlation function between ultra-high energy cosmic rays (UHECR) observed by Yakutsk and AGASA experiments, and most powerful BL Lacertae objects. We find significant correlations which correspond to the probability of statistical fluctuation less than $10^{-4}$, including penatly for selecting the subset of brightest BL Lacs. We conclude that some of BL Lacs are sources of the observed UHECR and present a list of most probable candidates.

Source: http://arxiv.org/abs/astro-ph/0102476v2

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Sep 24, 2013
09/13

by
G. F. Giudice; A. Riotto; I. Tkachev

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Many models of supersymmetry breaking, in the context of either supergravity or superstring theories, predict the presence of particles with Planck-suppressed couplings and masses around the weak scale. These particles are generically called moduli. The excessive production of moduli in the early Universe jeopardizes the successful predictions of nucleosynthesis. In this paper we show that the efficient generation of these dangerous relics is an unescapable consequence of a wide variety of...

Source: http://arxiv.org/abs/hep-ph/0103248v2

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Sep 19, 2013
09/13

by
A. Kashlinsky; I. I. Tkachev; J. Frieman

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We study the microwave background anisotropy due to superhorizon-size perturbations (the Grischuk-Zel'dovich effect) in open universes with negative spatial curvature. Using COBE results on the low-order temperature multipole moments, we find that if the homogeneity of the observable Universe arises from an early epoch of inflation, the present density parameter cannot differ from unity by more than the observed quadrupole anisotropy, $|1-\Omega_0| \alt Q \simeq 5\times 10^{-6}$. Thus,...

Source: http://arxiv.org/abs/astro-ph/9405024v1

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Sep 21, 2013
09/13

by
G. F. Giudice; A. Riotto; I. Tkachev

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Many models of supersymmetry breaking, in the context of either supergravity or superstring theories, predict the presence of particles with weak scale masses and Planck-suppressed couplings. Typical examples are the scalar moduli and the gravitino. Excessive production of such particles in the early Universe destroys the successful predictions of nucleosynthesis. In particular, the thermal production of these relics after inflation leads to a bound on the reheating temperature, T_{RH} <...

Source: http://arxiv.org/abs/hep-ph/9907510v1

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Sep 21, 2013
09/13

by
P. Sikivie; I. I. Tkachev; Yun Wang

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The spectrum of cold dark matter particles on Earth is expected to have peaks in velocity space associated with particles which are falling onto the Galaxy for the first time and with particles which have fallen in and out of the Galaxy only a small number of times in the past. We obtain estimates for the velocity magnitudes and the local densities of the particles in these peaks. To this end we use the secondary infall model of galactic halo formation which we have generalized to take account...

Source: http://arxiv.org/abs/astro-ph/9609022v1

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Sep 19, 2013
09/13

by
G. F. Giudice; A. Riotto; I. Tkachev

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The excessive production of gravitinos in the early universe destroys the successful predictions of nucleosynthesis. The thermal generation of gravitinos after inflation leads to the bound on the reheating temperature, T_{RH} < 10^9 GeV. However, it has been recently realized that the non-thermal generation of gravitinos in the early universe can be extremely efficient and overcome the thermal production by several orders of magnitude, leading to much tighter constraints on the reheating...

Source: http://arxiv.org/abs/hep-ph/9911302v2

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Sep 19, 2013
09/13

by
Alexander Kusenko; Vadim Kuzmin; Igor I. Tkachev

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The trilinear couplings of squarks and sleptons to the Higgs bosons can give rise to a spectrum of bound states with exotic quantum numbers, for example, those of a leptoquark.

Source: http://arxiv.org/abs/hep-ph/9801405v2

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Sep 18, 2013
09/13

by
P. Sikivie; I. I. Tkachev; Yun Wang

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The cold dark matter spectrum on earth is expected to have peaks in velocity space. We obtain estimates for the sizes and locations of these peaks. To this end we have generalized the secondary infall model of galactic halo formation to include angular momentum of the dark matter particles. This new model is still spherically symmetric and it has self-similar solutions. Our results are relevant to direct dark matter search experiments.

Source: http://arxiv.org/abs/astro-ph/9504052v1

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Sep 19, 2013
09/13

by
S. Khlebnikov; L. Kofman; A. Linde; I. Tkachev

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During preheating after inflation, parametric resonance rapidly generates very large fluctuations of scalar fields. In models where the inflaton field $\phi$ oscillates in a double-well potential and interacts with another scalar field $X$, fluctuations of X can keep the \phi to -\phi symmetry temporarily restored. If the coupling of \phi to X is much stronger than the inflaton self-coupling, the subsequent symmetry breaking is a first-order phase transition. We demonstrate the existence of...

Source: http://arxiv.org/abs/hep-ph/9804425v1

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Sep 22, 2013
09/13

by
K. Dolag; A. D. Dolgov; I. I. Tkachev

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We have found that the phase-space of a dark matter particles assembling a galactic halo in cosmological N-body simulations has well defined fine grained structure. Recently accreted particles form distinctive velocity streams with high density contrast. For fixed observer position these streams lead to peaks in velocity distribution. Overall structure is close to that emerging in the secondary infall model.

Source: http://arxiv.org/abs/1210.8009v1

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Sep 19, 2013
09/13

by
Edward W. Kolb; Antonio Riotto; Igor I. Tkachev

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If a first-order phase transition is terminated by collisions of new-phase bubbles, there will exist a period of nonequilibrium between the time bubbles collide and the time thermal equilibrium is established. We study the behavior of the order parameter during this phase. We find that large nonthermal fluctuations at this stage tend to restore symmetry, i.e., the order parameter is smaller than its eventual thermal equilibrium value. We comment on possible consequences for electroweak...

Source: http://arxiv.org/abs/astro-ph/9703119v1

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42

Sep 22, 2013
09/13

by
I. Tkachev; S. Khlebnikov; L. Kofman; A. Linde

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We investigate nonthermal phase transitions that may occur after post-inflationary preheating in a simple model of a two-component scalar field with the effective potential $\lambda (\phi_i^2 - {\rm v}^2)^2/4$, where $\phi_1$ is identified with the inflaton field. We use three-dimensional lattice simulations to investigate the full nonlinear dynamics of the model. Fluctuations of the fields generated during and after preheating temporarily make the effective potential convex in the $\phi_1$...

Source: http://arxiv.org/abs/hep-ph/9805209v2

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Sep 22, 2013
09/13

by
K. Dolag; D. Grasso; V. Springel; I. Tkachev

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Magnetic fields (MF) in the Local Supercluster (LSC) of galaxies may have profound consequences for the propagation of Ultra High Energy Cosmic Rays (UHECR). Faraday rotations measurements provide some informations about MF in compact clusters. However, very few is known about less dense regions and about the global structure of MF in the LSC. In order to get a better knowledge of these fields we are performing constrained magnetohydrodynamical simulations of the LSC magnetic field. We will...

Source: http://arxiv.org/abs/astro-ph/0308155v1

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Jun 27, 2018
06/18

by
Z. Berezhiani; A. D. Dolgov; I. I. Tkachev

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We show that emerging tension between the direct astronomical measurements at low redshifts and cosmological parameters deduced from the Planck measurements of the CMB anisotropies can be alleviated if the dark matter consists of two fractions, stable part being dominant and a smaller unstable fraction. The latter constitutes $\sim 10$ per cent at the recombination epoch if decays by now.

Topics: Cosmology and Nongalactic Astrophysics, Astrophysics

Source: http://arxiv.org/abs/1505.03644