17,794 research outputs found
Expanding the thermodynamical potential and the analysis of the possible phase diagram of deconfinement in FL model
The deconfinement phase transition is studied in the FL model at finite
temperature and chemical potential. At MFT approximation, the phase transition
can only be the first order in the whole phase plane. By a Landau
expansion we further study the phase transition order and the possible phase
diagram of deconfinement. We discuss the possibilities of second order phase
transitions in FL model. By our analysis the cubic term in the Landau expansion
could be cancelled by the high order fluctuations. By an ansatz of the Landau
parameters, we obtain the possible phase diagram with both first and second
order phase transition including the tricritical point which is similar to that
of the chiral phase transition.Comment: 7 pages, 8 figures, submitted to Chinese Physics
Quantum and Classical Orientational Ordering in Solid Hydrogen
We present a unified view of orientational ordering in phases I, II, and III
of solid hydrogen. Phases II and III are orientationally ordered, while the
ordering objects in phase II are angular momenta of rotating molecules, and in
phase III the molecules themselves. This concept provides quantitative
explanation of the vibron softening, libron and roton spectra, and increase of
the IR vibron oscillator strength in phase III. The temperature dependence of
the effective charge parallels the frequency shifts of the IR and Raman
vibrons. All three quantities are linear in the order parameter.Comment: Replaced with the final text, accepted for publication in PRL. 1 Fig.
added. Misc. text revision
Quantum Reciprocity Conjecture for the Non-Equilibrium Steady State
By considering the lack of history dependence in the non-equilibrium steady
state of a quantum system we are led to conjecture that in such a system, there
is a set of quantum mechanical observables whose retarded response functions
are insensitive to the arrow of time, and which consequently satisfy a quantum
analog of the Onsager reciprocity relations. Systems which satisfy this
conjecture can be described by an effective Free energy functional. We
demonstrate that the conjecture holds in a resonant level model of a multi-lead
quantum dot.Comment: References revised to take account of related work on Onsager
reciprocity in mesoscopics by Christen, and in hydrodynamics by Mclennan,
Dufty and Rub
Superconductivity in the Chalcogens up to Multimegabar Pressures
Highly sensitive magnetic susceptibility techniques were used to measure the
superconducting transition temperatures in S up to 231(5) GPa. S
transforms to a superconductor with T of 10 K and has a discontinuity in
T_c dependence at 160 GPa corresponding to bco to beta-Po phase transition.
Above this pressure T_c in S has a maximum reaching about 17.3(+/-0.5) K at 200
GPa and then slowly decreases with pressure to 15 K at 230 GPa.
This trend in the pressure dependence parallels the behavior of the heavier
members Se and Te. Superconductivity in Se was also observed from 15 to 25 GPa
with T_c changing from 4 to 6 K and above 150 GPa with T_c of 8 K.
Similiarities in the T_c dependences for S, Se, and Te, and the implications
for oxygen are discussed.Comment: 4 pages, 10 figure
Orbital-dependent metamagnetic response in Sr4Ru3O10
We show that the metamagnetic transition in SrRuO bifurcates
into two transitions as the field is rotated away from the conducting planes.
This two-step process comprises partial or total alignment of moments in
ferromagnetic bands followed by an itinerant metamagnetic transition whose
critical field increases with rotation. Evidence for itinerant metamagnetism is
provided by the Shubnikov-de Hass effect which shows a non-trivial evolution of
the geometry of the Fermi surface and an enhancement of the quasiparticles
effective-mass across the transition. The metamagnetic response of
SrRuO is orbital-dependent and involves ferromagnetic and
metamagnetic bands.Comment: Physical Review B (in press
The influence of baryons on the mass distribution of dark matter halos
Using a set of high-resolution N-body/SPH cosmological simulations with
identical initial conditions but run with different numerical setups, we
investigate the influence of baryonic matter on the mass distribution of dark
halos when radiative cooling is NOT included. We compare the concentration
parameters of about 400 massive halos with virial mass from \Msun to
\Msun. We find that the concentration parameters for the
total mass and dark matter distributions in non radiative simulations are on
average larger by ~3% and 10% than those in a pure dark matter simulation. Our
results indicate that the total mass density profile is little affected by a
hot gas component in the simulations. After carefully excluding the effects of
resolutions and spurious two-body heating between dark matter and gas
particles, we conclude that the increase of the dark matter concentration
parameters is due to interactions between baryons and dark matter. We
demonstrate this with the aid of idealized simulations of two-body mergers. The
results of individual halos simulated with different mass resolutions show that
the gas profiles of densities, temperature and entropy are subjects of mass
resolution of SPH particles. In particular, we find that in the inner parts of
halos, as the SPH resolution increases the gas density becomes higher but both
the entropy and temperature decrease.Comment: 8 pages, 6 figures, 1 table, ApJ in press (v652n1); updated to match
with the being published versio
Effects of Dust on Gravitational Lensing by Spiral Galaxies
Gravitational lensing of an optical QSO by a spiral galaxy is often
counteracted by dust obscuration, since the line-of-sight to the QSO passes
close to the center of the galactic disk. The dust in the lens is likely to be
correlated with neutral hydrogen, which in turn should leave a Lyman-alpha
absorption signature on the QSO spectrum. We use the estimated dust-to-gas
ratio of the Milky-Way galaxy as a mean and allow a spread in its values to
calculate the effects of dust on lensing by low redshift spiral galaxies. Using
a no-evolution model for spirals at z<1 we find (in Lambda=0 cosmologies) that
the magnification bias due to lensing is stronger than dust obscuration for QSO
samples with a magnitude limit B<16. The density parameter of neutral hydrogen,
Omega_HI, is overestimated in such samples and is underestimated for fainter
QSOs.Comment: 18 pages, 4 figures, ApJ, in pres
Anisotropy of magnetothermal conductivity in Sr2RuO4
The dependence of in-plane and interplane thermal conductivities of Sr2RuO4
on temperature, as well as magnetic field strength and orientation, is
reported. We found no notable anisotropy in the thermal conductivity for the
magnetic field rotation parallel to the conducting plane in the whole range of
experimental temperatures and fields, except in the vicinity of the upper
critical field Hc2, where the anisotropy of the Hc2 itself plays a dominant
role. This finding imposes strong constraints on the possible models of
superconductivity in Sr2RuO4 and supports the existence of a superconducting
gap with a line of nodes running orthogonal to the Fermi surface cylinder.Comment: published in Phys. Rev. Lett. 4pages, 4 eps figures, LaTe
Experimental determination of superconducting parameters for the intermetallic perovskite superconductor ${\text {MgCNi}}_3
We have measured upper-critical-field , specific heat C, and
tunneling spectra of the intermetallic perovskite superconductor MgCNi
with a superconducting transition temperature K. Based
on these measurements and relevant theoretical relations, we have evaluated
various superconducting parameters for this material, including the
thermodynamic critical field (0), coherence length (0),
penetration depth (0), lower-critical-field (0), and
Ginsberg-Landau parameter (0). From the specific heat, we obtain the
Debye temperature 280 K. We find a jump of
=2.3 at (where is the
normal state electronic specific coefficient), which is much larger than the
weak coupling BCS value of 1.43. Our tunneling measurements revealed a gap
feature in the tunneling spectra at with 4.6, again larger than the weak-coupling value
of 3.53. Both findings indicate that MgCNi is a strong-coupling
superconductor. In addition, we observed a pronounced zero-bias conductance
peak (ZBCP) in the tunneling spectra.
We discuss the possible physical origins of the observed ZBCP, especially in
the context of the pairing symmetry of the material.Comment: 5 pages, 4 figure
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