384 research outputs found
Evolution of the Order Parameter after Bubble Collisions
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 baryogenesis.Comment: 11 page LaTeX file with two figures, fig1.ps and fig2.p
Ultra High Energy Cosmic Rays and Inflation Relics
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.Comment: Submitted to Physics Report
Quantum phase slips in a confined geometry
We consider tunneling of vortices across a superconducting film that is both
narrow and short (and connected to bulk superconducting leads at the ends). We
find that in the superconducting state the resistance, at low values of the
temperature (T) and current, does not follow the power-law dependence on T
characteristic of longer samples but is exponential in 1/T. The coefficient of
1/T in the exponent depends on the length or, equivalently, the total
normal-state resistance of the sample. These conclusions persist in the
one-dimensional limit, which is similar to the problem of quantum phase slips
in an ultra-narrow short wire.Comment: 14 pages, 1 figure; published in Phys. Rev.
Recommendations on reforming the current legislation on the import and export of research materials
The article provides the analysis of the current state in importing and exporting of materials for research and development activity, its problems and prospects of further development. The authors note the imperfection of the legislation in this area and offer a wide range of recommendations for qualitative improvement of the situation. The relevance of the research topic is determined by the fact that in the 21st century the role and place of Russian Federation in the world economy would largely depend on the level of its scientific and technological development, the ability to create and effectively replicate its own achievements and make extensive use of imported high-end technologies, the degree of its presence on the world market of high and new technologies.peer-reviewe
First-order nonthermal phase transition after preheating
During preheating after inflation, parametric resonance rapidly generates
very large fluctuations of scalar fields. In models where the inflaton field
oscillates in a double-well potential and interacts with another scalar
field , 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 this nonthermal phase transition
with lattice simulations of the full nonlinear dynamics of the interacting
fields. In particular, we observe nucleation of an expanding bubble.Comment: RevTeX, 4 page
Quantum Dew
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.Comment: 4 pages, revtex, 5 figure
Quantum phase slips in the presence of finite-range disorder
To study the effect of disorder on quantum phase slips (QPS) in
superconducting wires, we consider the plasmon-only model where disorder can be
incorporated into a first-principles instanton calculation. We consider weak
but general finite-range disorder and compute the formfactor in the QPS rate
associated with momentum transfer. We find that the system maps onto
dissipative quantum mechanics, with the dissipative coefficient controlled by
the wave (plasmon) impedance Z of the wire and with a superconductor-insulator
transition at Z=6.5 kOhm. We speculate that the system will remain in this
universality class after resistive effects at the QPS core are taken into
account.Comment: 4 pages, as accepted at Phys. Rev. Letter
International students academic mobility automatization in higher education establishments
The research is dedicated to the question of international studentsтacademic mobility automatization due to engineering and design of the special information system. This system should minimize the role of an expert at each stage of mobility support. Some features of such system are considered in the paper.В докладе рассматривается вопрос автоматизации международной студенческой академической мобильности за счёт разработки и внедрения информационной системы, минимизирующей участие эксперта в процессе сопровождения мобильности. Выдвинуты идеи относительно составных модулей такой системы
Patterns from preheating
The formation of regular patterns is a well-known phenomenon in condensed
matter physics. Systems that exhibit pattern formation are typically driven and
dissipative with pattern formation occurring in the weakly non-linear regime
and sometimes even in more strongly non-linear regions of parameter space. In
the early universe, parametric resonance can drive explosive particle
production called preheating. The fields that are populated then decay quantum
mechanically if their particles are unstable. Thus, during preheating, a
driven-dissipative system exists. In this paper, we show that a self-coupled
inflaton oscillating in its potential at the end of inflation can exhibit
pattern formation.Comment: 4 pages, RevTex, 6 figure
Preheating of the nonminimally coupled inflaton field
We investigate preheating of an inflaton field coupled nonminimally to
a spacetime curvature. In the case of a self-coupling inflaton potential
, the dynamics of preheating changes by the effect of
the negative . We find that the nonminimal coupling works in two ways.
First, since the initial value of inflaton field for reheating becomes
smaller with the increase of , the evolution of the inflaton quanta is
delayed for fixed . Second, the oscillation of the inflaton field is
modified and the nonadiabatic change around occurs significantly. That
makes the resonant band of the fluctuation field wider. Especially for strong
coupling regimes , the growth of the inflaton flutuation is
dominated by the resonance due to the nonminimal coupling, which leads to the
significant enhancement of low momentum modes. Although the final variance of
the inflaton fluctuation does notchange significantly compared with the
minimally coupled case, we have found that the energy transfer from the
homogeneous inflaton to created particles efficiently occurs for .Comment: 13pages, 11figure
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