6,556 research outputs found
SM(2,4k) fermionic characters and restricted jagged partitions
A derivation of the basis of states for the superconformal minimal
models is presented. It relies on a general hypothesis concerning the role of
the null field of dimension . The basis is expressed solely in terms of
modes and it takes the form of simple exclusion conditions (being thus a
quasi-particle-type basis). Its elements are in correspondence with
-restricted jagged partitions. The generating functions of the latter
provide novel fermionic forms for the characters of the irreducible
representations in both Ramond and Neveu-Schwarz sectors.Comment: 12 page
New path description for the M(k+1,2k+3) models and the dual Z_k graded parafermions
We present a new path description for the states of the non-unitary
M(k+1,2k+3) models. This description differs from the one induced by the
Forrester-Baxter solution, in terms of configuration sums, of their
restricted-solid-on-solid model. The proposed path representation is actually
very similar to the one underlying the unitary minimal models M(k+1,k+2), with
an analogous Fermi-gas interpretation. This interpretation leads to fermionic
expressions for the finitized M(k+1,2k+3) characters, whose infinite-length
limit represent new fermionic characters for the irreducible modules. The
M(k+1,2k+3) models are also shown to be related to the Z_k graded parafermions
via a (q to 1/q) duality transformation.Comment: 43 pages (minor typo corrected and minor rewording in the
introduction
Neutron star radii and crusts: uncertainties and unified equations of state
The uncertainties in neutron star (NS) radii and crust properties due to our
limited knowledge of the equation of state (EOS) are quantitatively analysed.
We first demonstrate the importance of a unified microscopic description for
the different baryonic densities of the star. If the pressure functional is
obtained matching a crust and a core EOS based on models with different
properties at nuclear matter saturation, the uncertainties can be as large as
for the crust thickness and for the radius. Necessary
conditions for causal and thermodynamically consistent matchings between the
core and the crust are formulated and their consequences examined. A large set
of unified EOS for purely nucleonic matter is obtained based on 24 Skyrme
interactions and 9 relativistic mean-field nuclear parametrizations. In
addition, for relativistic models 17 EOS including a transition to hyperonic
matter at high density are presented. All these EOS have in common the property
of describing a star and of being causal within stable NS. A span
of km and km is obtained for the radius of, respectively,
and star. Applying a set of nine further
constraints from experiment and ab-initio calculations the uncertainty is
reduced to km and km, respectively. These residual uncertainties
reflect lack of constraints at large densities and insufficient information on
the density dependence of the EOS near the nuclear matter saturation point. The
most important parameter to be constrained is shown to be the symmetry energy
slope which exhibits a linear correlation with the stellar radius,
particularly for masses . Potential constraints on , the
NS radius and the EOS from observations of thermal states of NS are also
discussed. [Abriged]Comment: Submitted to Phys. Rev. C. Supplemental material not include
Recent developments in the determination of the amplitude and phase of quantum oscillations for the linear chain of coupled orbits
De Haas-van Alphen oscillations are studied for Fermi surfaces (FS)
illustrating the model proposed by Pippard in the early sixties, namely the
linear chain of orbits coupled by magnetic breakdown. This FS topology is
relevant for many multiband quasi-two dimensional (q-2D) organic metals such as
-(BEDT-TTF)Cu(NCS) and
-(BEDT-TTF)CoBr(CHCl) which are considered in
detail. Whereas the Lifshits-Kosevich model only involves a first order
development of field- and temperature-dependent damping factors, second order
terms may have significant contribution on the Fourier components amplitude for
such q-2D systems at high magnetic field and low temperature. The strength of
these second order terms depends on the relative value of the involved damping
factors, which are in turns strongly dependent on parameters such as the
magnetic breakdown field, effective masses and, most of all, effective
Land\'{e} factors. In addition, the influence of field-dependent Onsager phase
factors on the oscillation spectra is considered.Comment: arXiv admin note: text overlap with arXiv:1304.665
New bases for a general definition for the moving preferred basis
One of the challenges of the Environment-Induced Decoherence (EID) approach
is to provide a simple general definition of the moving pointer basis or moving
preferred basis. In this letter we prove that the study of the poles that
produce the decaying modes in non-unitary evolution, could yield a general
definition of the relaxation, the decoherence times, and the moving preferred
basis. These probably are the most important concepts in the theory of
decoherence, one of the most relevant chapters of theoretical (and also
practical) quantum mechanics. As an example we solved the Omnes (or
Lee-Friedrich) model using our theory.Comment: 6 page
Thermalisation time and specific heat of neutron stars crust
We discuss the thermalisation process of the neutron stars crust described by
solving the heat transport equation with a microscopic input for the specific
heat of baryonic matter. The heat equation is solved with initial conditions
specific to a rapid cooling of the core. To calculate the specific heat of
inner crust baryonic matter, i.e., nuclear clusters and unbound neutrons, we
use the quasiparticle spectrum provided by the Hartree-Fock-Bogoliubov approach
at finite temperature. In this framework we analyse the dependence of the crust
thermalisation on pairing properties and on cluster structure of inner crust
matter. It is shown that the pairing correlations reduce the crust
thermalisation time by a very large fraction. The calculations show also that
the nuclear clusters have a non-negligible influence on the time evolution of
the surface temperature of the neutron star.Comment: 7 pages, 5 figures, submitted to Phys. Rev.
Observation of Magnetic Supercooling of the Transition to the Vortex State
We demonstrate that the transition from the high-field state to the vortex
state in a nanomagnetic disk shows the magnetic equivalent of supercooling.
This is evidence that this magnetic transition can be described in terms of a
modified Landau first-order phase transition. To accomplish this we have
measured the bulk magnetization of single magnetic disks using nanomechanical
torsional resonator torque magnetometry. This allows observation of single
vortex creation events without averaging over an array of disks or over
multiple runs.Comment: 11 pages preprint, 4 figures, accepted to New Journal of Physic
On Critical Velocities in Exciton Superfluidity
The presence of exciton phonon interactions is shown to play a key role in
the exciton superfluidity. We apply the Landau criterion for an exciton-phonon
condensate moving uniformly at zero temperature. It turns out that there are
essentially two critical velocities in the theory. Within the range of these
velocities the condensate can exist only as a bright soliton. The excitation
spectrum and differential equations for the wave function of this condensate
are derived.Comment: 7 pages, Latex; to be published in Phys.Rev.Lett (1997
Random site dilution properties of frustrated magnets on a hierarchical lattice
We present a method to analyze magnetic properties of frustrated Ising spin
models on specific hierarchical lattices with random dilution. Disorder is
induced by dilution and geometrical frustration rather than randomness in the
internal couplings of the original Hamiltonian. The two-dimensional model
presented here possesses a macroscopic entropy at zero temperature in the large
size limit, very close to the Pauling estimate for spin-ice on pyrochlore
lattice, and a crossover towards a paramagnetic phase. The disorder due to
dilution is taken into account by considering a replicated version of the
recursion equations between partition functions at different lattice sizes. An
analysis at first order in replica number allows for a systematic
reorganization of the disorder configurations, leading to a recurrence scheme.
This method is numerically implemented to evaluate the thermodynamical
quantities such as specific heat and susceptibility in an external field.Comment: 26 pages, 11 figure
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