1,789 research outputs found
Analytical theory for proton correlations in common water ice
We provide a fully analytical microscopic theory for the proton correlations
in water ice . We compute the full diffuse elastic neutron scattering
structure factor, which we find to be in excellent quantitative agreement with
Monte Carlo simulations. It is also in remarkable qualitative agreement with
experiment, in the absence of any fitting parameters. Our theory thus provides
a tractable analytical starting point to account for more delicate features of
the proton correlations in water ice. In addition, it directly determines an
effective field theory of water ice as a topological phase.Comment: 5 pages, 3 figure
Surface Impedance Determination via Numerical Resolution of the Inverse Helmholtz Problem
Assigning boundary conditions, such as acoustic impedance, to the frequency
domain thermoviscous wave equations (TWE), derived from the linearized
Navier-Stokes equations (LNSE) poses a Helmholtz problem, solution to which
yields a discrete set of complex eigenfunctions and eigenvalue pairs. The
proposed method -- the inverse Helmholtz solver (iHS) -- reverses such
procedure by returning the value of acoustic impedance at one or more unknown
impedance boundaries (IBs) of a given domain, via spatial integration of the
TWE for a given real-valued frequency with assigned conditions on other
boundaries. The iHS procedure is applied to a second-order spatial
discretization of the TWEs on an unstructured staggered grid arrangement. Only
the momentum equation is extended to the center of each IB face where pressure
and velocity components are co-located and treated as unknowns. The iHS is
finally closed via assignment of the surface gradient of pressure phase over
the IBs, corresponding to assigning the shape of the acoustic waveform at the
IB. The iHS procedure can be carried out independently for different
frequencies, making it embarrassingly parallel, and able to return the complete
broadband complex impedance distribution at the IBs in any desired frequency
range to arbitrary numerical precision. The iHS approach is first validated
against Rott's theory for viscous rectangular and circular ducts. The impedance
of a toy porous cavity with a complex geometry is then reconstructed and
validated with companion fully compressible unstructured Navier-Stokes
simulations resolving the cavity geometry. Verification against one-dimensional
impedance test tube calculations based on time-domain impedance boundary
conditions (TDIBC) is also carried out. Finally, results from a preliminary
analysis of a thermoacoustically unstable cavity are presented.Comment: As submitted to AIAA Aviation 201
On the isospin dependence of the mean spin-orbit field in nuclei
By the use of the latest experimental data on the spectra of Sb and
Sn and on the analysis of properties of other odd nuclei adjacent to
doubly magic closed shells the isospin dependence of a mean spin-orbit
potential is defined. Such a dependence received the explanation in the
framework of different theoretical approaches.Comment: 52 pages, Revtex, no figure
Topological Entanglement Entropy of a Bose-Hubbard Spin Liquid
The Landau paradigm of classifying phases by broken symmetries was
demonstrated to be incomplete when it was realized that different quantum Hall
states could only be distinguished by more subtle, topological properties.
Today, the role of topology as an underlying description of order has branched
out to include topological band insulators, and certain featureless gapped Mott
insulators with a topological degeneracy in the groundstate wavefunction.
Despite intense focus, very few candidates for these topologically ordered
"spin liquids" exist. The main difficulty in finding systems that harbour spin
liquid states is the very fact that they violate the Landau paradigm, making
conventional order parameters non-existent. Here, we uncover a spin liquid
phase in a Bose-Hubbard model on the kagome lattice, and measure its
topological order directly via the topological entanglement entropy. This is
the first smoking-gun demonstration of a non-trivial spin liquid, identified
through its entanglement entropy as a gapped groundstate with emergent Z2 gauge
symmetry.Comment: 4+ pages, 3 figure
Conductance and Shot Noise for Particles with Exclusion Statistics
The first quantized Landauer approach to conductance and noise is generalized
to particles obeying exclusion statistics. We derive an explicit formula for
the crossover between the shot and thermal noise limits and argue that such a
crossover can be used to determine experimentally whether charge carriers in
FQHE devices obey exclusion statistics.Comment: 4 pages, revtex, 1 eps figure include
Rigorous Analysis of Singularities and Absence of Analytic Continuation at First Order Phase Transition Points in Lattice Spin Models
We report about two new rigorous results on the non-analytic properties of
thermodynamic potentials at first order phase transition. The first one is
valid for lattice models () with arbitrary finite state space, and
finite-range interactions which have two ground states. Under the only
assumption that the Peierls Condition is satisfied for the ground states and
that the temperature is sufficiently low, we prove that the pressure has no
analytic continuation at the first order phase transition point. The second
result concerns Ising spins with Kac potentials
, where is a small scaling
parameter, and a fixed finite range potential. In this framework, we
relate the non-analytic behaviour of the pressure at the transition point to
the range of interaction, which equals . Our analysis exhibits a
crossover between the non-analytic behaviour of finite range models
() and analyticity in the mean field limit (). In
general, the basic mechanism responsible for the appearance of a singularity
blocking the analytic continuation is that arbitrarily large droplets of the
other phase become stable at the transition point.Comment: 4 pages, 2 figure
Spin ice in a field: quasi-phases and pseudo-transitions
Thermodynamics of the short-range model of spin ice magnets in a field is
considered in the Bethe - Peierls approximation. The results obtained for
[111], [100] and [011] fields agrees reasonably well with the existing
Monte-Carlo simulations and some experiments. In this approximation all
extremely sharp field-induced anomalies are described by the analytical
functions of temperature and applied field. In spite of the absence of true
phase transitions the analysis of the entropy and specific heat reliefs over
H-T plane allows to discern the "pseudo-phases" with specific character of spin
fluctuations and define the lines of more or less sharp "pseudo-transitions"
between them.Comment: 18 pages, 16 figure
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