9,231 research outputs found
On an exact hydrodynamic solution for the elliptic flow
Looking for the underlying hydrodynamic mechanisms determining the elliptic
flow we show that for an expanding relativistic perfect fluid the transverse
flow may derive from a solvable hydrodynamic potential, if the entropy is
transversally conserved and the corresponding expansion "quasi-stationary",
that is mainly governed by the temperature cooling. Exact solutions for the
velocity flow coefficients and the temperature dependence of the spatial
and momentum anisotropy are obtained and shown to be in agreement with the
elliptic flow features of heavy-ion collisions.Comment: 10 pages, 4 figure
Nonequilibrium evolution thermodynamics
A new approach - nonequilibrium evolution thermodynamics, is compared with
classical variant of Landau approachComment: 4 pages, 1 figur
Polarons in suspended carbon nanotubes
We prove theoretically the possibility of electric-field controlled polaron
formation involving flexural (bending) modes in suspended carbon nanotubes.
Upon increasing the field, the ground state of the system with a single extra
electron undergoes a first order phase transition between an extended state and
a localized polaron state. For a common experimental setup, the threshold
electric field is only of order V/m
Relativistic Theory of Hydrodynamic Fluctuations with Applications to Heavy Ion Collisions
We develop the relativistic theory of hydrodynamic fluctuations for
application to high energy heavy ion collisions. In particular, we investigate
their effect on the expanding boost-invariant (Bjorken) solution of the
hydrodynamic equations. We discover that correlations over a long rapidity
range are induced by the propagation of the sound modes. Due to the expansion,
the dispersion law for these modes is non-linear and attenuated even in the
limit of zero viscosity. As a result, there is a non-dissipative wake behind
the sound front which is generated by any instantaneous point-like fluctuation.
We evaluate the two-particle correlators using the initial conditions and
hydrodynamic parameters relevant for heavy-ion collisions at RHIC and LHC. In
principle these correlators can be used to obtain information about the
viscosities because the magnitudes of the fluctuations are directly
proportional to them.Comment: 39 pages, 6 figures; references adde
Pulsars: Gigantic Nuclei
What is the real nature of pulsars? This is essentially a question of the
fundamental strong interaction between quarks at low-energy scale and hence of
the non-perturbative quantum chromo-dynamics, the solution of which would
certainly be meaningful for us to understand one of the seven millennium prize
problems (i.e., "Yang-Mills Theory") named by the Clay Mathematical Institute.
After a historical note, it is argued here that a pulsar is very similar to an
extremely big nucleus, but is a little bit different from the {\em gigantic
nucleus} speculated 80 years ago by L. Landau. The paper demonstrates the
similarity between pulsars and gigantic nuclei from both points of view: the
different manifestations of compact stars and the general behavior of the
strong interaction.Comment: 8 pages, 1 figures; Comments welcome
Detection of spin injection into a double quantum dot: Violation of magnetic-field-inversion symmetry of nuclear polarization instabilities
In mesoscopic systems with spin-orbit coupling, spin-injection into quantum
dots at zero magnetic field is expected under a wide range of conditions.
However, up to now, a viable approach for experimentally identifying such
injection has been lacking. We show that electron spin injection into a
spin-blockaded double quantum dot is dramatically manifested in the breaking of
magnetic- field-inversion symmetry of nuclear polarization instabilities. Over
a wide range of parameters, the asymmetry between positive and negative
instability fields is extremely sensitive to the injected electron spin
polarization and allows for the detection of even very weak spin injection.
This phenomenon may be used to investigate the mechanisms of spin transport,
and may hold implications for spin-based information processing
Evaluation of specific heat for superfluid helium between 0 - 2.1 K based on nonlinear theory
The specific heat of liquid helium was calculated theoretically in the Landau
theory. The results deviate from experimental data in the temperature region of
1.3 - 2.1 K. Many theorists subsequently improved the results of the Landau
theory by applying temperature dependence of the elementary excitation energy.
As well known, many-body system has a total energy of Galilean covariant form.
Therefore, the total energy of liquid helium has a nonlinear form for the
number distribution function. The function form can be determined using the
excitation energy at zero temperature and the latent heat per helium atom at
zero temperature. The nonlinear form produces new temperature dependence for
the excitation energy from Bose condensate. We evaluate the specific heat using
iteration method. The calculation results of the second iteration show good
agreement with the experimental data in the temperature region of 0 - 2.1 K,
where we have only used the elementary excitation energy at 1.1 K.Comment: 6 pages, 3 figures, submitted to Journal of Physics: Conference
Serie
Critical phenomena and phase sequence in classical bilayer Wigner crystal at zero temperature
We study the ground-state properties of a system of identical classical
Coulombic point particles, evenly distributed between two equivalently charged
parallel plates at distance ; the system as a whole is electroneutral. It
was previously shown that upon increasing d from 0 to infinity, five different
structures of the bilayer Wigner crystal become energetically favored, starting
from a hexagonal lattice (phase I, d=0) and ending at a staggered hexagonal
lattice (phase V, d -> infinity). In this paper, we derive new series
representations of the ground-state energy for all five bilayer structures. The
derivation is based on a sequence of transformations for lattice sums of
Coulomb two-particle potentials plus the neutralizing background, having their
origin in the general theory of Jacobi theta functions. The new series provide
convenient starting points for both analytical and numerical progress. Its
convergence properties are indeed excellent: Truncation at the fourth term
determines in general the energy correctly up to 17 decimal digits. The
accurate series representations are used to improve the specification of
transition points between the phases and to solve a controversy in previous
studies. In particular, it is shown both analytically and numerically that the
hexagonal phase I is stable only at d=0, and not in a finite interval of small
distances between the plates as was anticipated before. The expansions of the
structure energies around second-order transition points can be done
analytically, which enables us to show that the critical behavior is of the
Ginzburg-Landau type, with a mean-field critical index beta=1/2 for the growth
of the order parameters
Exact solutions of classical scalar field equations
We give a class of exact solutions of quartic scalar field theories. These
solutions prove to be interesting as are characterized by the production of
mass contributions arising from the nonlinear terms while maintaining a
wave-like behavior. So, a quartic massless equation has a nonlinear wave
solution with a dispersion relation of a massive wave and a quartic scalar
theory gets its mass term renormalized in the dispersion relation through a
term depending on the coupling and an integration constant. When spontaneous
breaking of symmetry is considered, such wave-like solutions show how a mass
term with the wrong sign and the nonlinearity give rise to a proper dispersion
relation. These latter solutions do not change the sign maintaining the
property of the selected value of the equilibrium state. Then, we use these
solutions to obtain a quantum field theory for the case of a quartic massless
field. We get the propagator from a first order correction showing that is
consistent in the limit of a very large coupling. The spectrum of a massless
quartic scalar field theory is then provided. From this we can conclude that,
for an infinite countable number of exact classical solutions, there exist an
infinite number of equivalent quantum field theories that are trivial in the
limit of the coupling going to infinity.Comment: 7 pages, no figures. Added proof of existence of a zero mode and two
more references. Accepted for publication in Journal of Nonlinear
Mathematical Physic
A new collective mode in the fractional quantum Hall liquid
We apply the methods of continuum mechanics to the study of the collective
modes of the fractional quantum Hall liquid. Our main result is that at long
wavelength there are {\it two} distinct modes of oscillations, while previous
theories predicted only {\it one}. The two modes are shown to arise from the
internal dynamics of shear stresses created by the Coulomb interaction in the
liquid. Our prediction is supported by recent light scattering experiments,
which report the observation of two long-wavelength modes in a quantum Hall
liquid.Comment: 4 pages, 1 Figur
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