On initial conditions for the Hot Big Bang

We analyse the process of reheating the Universe in the electroweak theory where the Higgs field plays a role of the inflaton. We estimate the maximal temperature of the Universe and fix the initial conditions for radiation-dominated phase of the Universe expansion in the framework of the Standard Model (SM) and of the nuMSM -- the minimal extension of the SM by three right-handed singlet fermions. We show that the inflationary epoch is followed by a matter dominated stage related to the Higgs field oscillations. We investigate the energy transfer from Higgs-inflaton to the SM particles and show that the radiation dominated phase of the Universe expansion starts at temperature T_r~(3-15)*10^{13} GeV, where the upper bound depends on the Higgs boson mass. We estimate the production rate of singlet fermions at preheating and find that their concentrations at T_r are negligibly small. This suggests that the sterile neutrino Dark Matter (DM) production and baryogenesis in the nuMSM with Higgs-driven inflation are low energy phenomena, having nothing to do with inflation. We study then a modification of the nuMSM, adding to its Lagrangian higher dimensional operators suppressed by the Planck scale. The role of these operators in Higgs-driven inflation is clarified. We find that these operators do not contribute to the production of Warm Dark Matter (WDM) and to baryogenesis. We also demonstrate that the sterile neutrino with mass exceeding 100 keV (a Cold Dark Matter (CDM) candidate) can be created during the reheating stage of the Universe in necessary amounts. We argue that the mass of DM sterile neutrino should not exceed few MeV in order not to overclose the Universe.Comment: 41 pages, 5 figures. Journal version accepted in JCA

Standard Model Higgs boson mass from inflation: two loop analysis

We extend the analysis of \cite{Bezrukov:2008ej} of the Standard Model Higgs inflation accounting for two-loop radiative corrections to the effective potential. As was expected, higher loop effects result in some modification of the interval for allowed Higgs masses m_min<m_H<m_max, which somewhat exceeds the region in which the Standard Model can be considered as a viable effective field theory all the way up to the Planck scale. The dependence of the index n_s of scalar perturbations on the Higgs mass is computed in two different renormalization procedures, associated with the Einstein (I) and Jordan (II) frames. In the procedure I the predictions of the spectral index of scalar fluctuations and of the tensor-to-scalar ratio practically do not depend on the Higgs mass within the admitted region and are equal to n_s=0.97 and r=0.0034 respectively. In the procedure II the index n_s acquires the visible dependence on the Higgs mass and and goes out of the admitted interval at m_H below m_min. We compare our findings with the results of \cite{DeSimone:2008ei}.Comment: 24 paged, 9 figures. Journal version (typos fixed, expanded discussions

Dark energy and dark matter from nonlocal ghost-free gravity theory

We suggest a class of generally covariant ghost-free nonlocal gravity models generating de Sitter or Anti-de Sitter background with an arbitrary value of the effective cosmological constant and featuring a mechanism of dark matter simulation. These models interpolate between the general relativistic phase on a flat spacetime background and their strongly coupled infrared (Anti)-de Sitter phase with two propagating massless graviton modes.Comment: 9 pages, LaTeX, final version published in Phys. Lett. B: title changed, discussion of Schwinger-Keldysh technique vs Euclidean field theory extended, presentation improved, references added. arXiv admin note: substantial text overlap with arXiv:1112.434

Fluctuations and Dissipation of Coherent Magnetization

A quantum mechanical model is used to derive a generalized Landau-Lifshitz equation for a magnetic moment, including fluctuations and dissipation. The model reproduces the Gilbert-Brown form of the equation in the classical limit. The magnetic moment is linearly coupled to a reservoir of bosonic degrees of freedom. Use of generalized coherent states makes the semiclassical limit more transparent within a path-integral formulation. A general fluctuation-dissipation theorem is derived. The magnitude of the magnetic moment also fluctuates beyond the Gaussian approximation. We discuss how the approximate stochastic description of the thermal field follows from our result. As an example, we go beyond the linear-response method and show how the thermal fluctuations become anisotropy-dependent even in the uniaxial case.Comment: 22 page

Open inflation from quantum cosmology with a strong nonminimal coupling

We propose the mechanism of quantum creation of the open Universe in the observable range of values of $\Omega$. This mechanism is based on the no-boundary quantum state with the Hawking-Turok instanton applied to the model with a strong nonminimal coupling of the inflaton field. We develop the slow roll perturbation expansion for the instanton solution and obtain a nontrivial contribution to the classical instanton action. The interplay of this classical contribution with the loop effects due to quantum effective action generates the probability distribution peak with necessary parameters of the inflation stage without invoking any anthropic considerations. In contrast with a similar mechanism for closed models, existing only for the tunneling quantum state of the Universe, the observationally justified open inflation originates from the no-boundary cosmological wavefunction.Comment: 28 pages, LaTe

Aspects of the FM Kondo Model: From Unbiased MC Simulations to Back-of-an-Envelope Explanations

Effective models are derived from the ferromagnetic Kondo lattice model with classical corespins, which greatly reduce the numerical effort. Results for these models are presented. They indicate that double exchange gives the correct order of magnitude and the correct doping dependence of the Curie temperature. Furthermore, we find that the jump in the particle density previously interpreted as phase separation is rather explained by ferromagnetic polarons.Comment: Proceedings of Wandlitz Days of Magnetism 200

Effective equations of motion and initial conditions for inflation in quantum cosmology

We obtain effective equations of inflationary dynamics for the mean inflaton and metric fields in the no-boundary and tunneling quantum states of the Universe. In the slow roll approximation (taking the form of the local Schwiger-DeWitt expansion) effective equations follow from the Euclidean effective action on the DeSitter gravitational instanton. Effective equations are applied in the model of the inflaton scalar field coupled to the GUT sector of matter fields and also having a strong nonminimal coupling to the curvature. The inverse of its big negative nonminimal coupling constant, serves as a small parameter of the slow roll expansion and semiclassical expansion of quantum gravitational effects. As a source of initial conditions we use a sharp probability peak recently obtained in the one-loop approximation for the no-boundary and tunneling quantum states and belonging (in virtue of a strong nonminimal coupling) to the GUT energy scale much below the Planck scale. The obtained equations in the tunneling quantum state predict a finite duration of inflationary stage compatible with the observational status of inflation theory, whereas for the no-boundary state they lead to the infinite inflationary epoch with a constant inflaton field.Comment: 23 pages, LaTe

Universality of the thermodynamic Casimir effect

Recently a nonuniversal character of the leading spatial behavior of the thermodynamic Casimir force has been reported [X. S. Chen and V. Dohm, Phys. Rev. E {\bf 66}, 016102 (2002)]. We reconsider the arguments leading to this observation and show that there is no such leading nonuniversal term in systems with short-ranged interactions if one treats properly the effects generated by a sharp momentum cutoff in the Fourier transform of the interaction potential. We also conclude that lattice and continuum models then produce results in mutual agreement independent of the cutoff scheme, contrary to the aforementioned report. All results are consistent with the {\em universal} character of the Casimir force in systems with short-ranged interactions. The effects due to dispersion forces are discussed for systems with periodic or realistic boundary conditions. In contrast to systems with short-ranged interactions, for $L/\xi \gg 1$ one observes leading finite-size contributions governed by power laws in $L$ due to the subleading long-ranged character of the interaction, where $L$ is the finite system size and $\xi$ is the correlation length.Comment: 11 pages, revtex, to appear in Phys. Rev. E 68 (2003

Current-spin-density functional study of persistent currents in quantum rings

We present a numerical study of persistent currents in quantum rings using current spin density functional theory (CSDFT). This formalism allows for a systematic study of the joint effects of both spin, interactions and impurities for realistic systems. It is illustrated that CSDFT is suitable for describing the physical effects related to Aharonov-Bohm phases by comparing energy spectra of impurity-free rings to existing exact diagonalization and experimental results. Further, we examine the effects of a symmetry-breaking impurity potential on the density and current characteristics of the system and propose that narrowing the confining potential at fixed impurity potential will suppress the persistent current in a characteristic way.Comment: 7 pages REVTeX, including 8 postscript figure

The leading particle effect from light quark fragmentation in charm hadroproduction

The asymmetry of $D^-$ and $D^+$ meson production in $\pi^-N$ scattering observed by the E791 experiment is a typical phenomenon known as the leading particle effect in charm hadroproducton. We show that the phenomenon can be explained by the effect of light quark fragmentation into charmed hadrons (LQF). Meanwhile, the size of the LQF effect is estimated from data of the E791 experiment. A comparison is made with the estimate of the LQF effect from prompt like-sign dimuon rate in neutrino experiments. The influence of the LQF effect on the measurement of nucleon strange distribution asymmetry from charged current charm production processes is briefly discussed.Comment: 6 latex pages, 1 figure, to appear in EPJ