1,314 research outputs found
Semiclassical Description of Tunneling in Mixed Systems: The Case of the Annular Billiard
We study quantum-mechanical tunneling between symmetry-related pairs of
regular phase space regions that are separated by a chaotic layer. We consider
the annular billiard, and use scattering theory to relate the splitting of
quasi-degenerate states quantized on the two regular regions to specific paths
connecting them. The tunneling amplitudes involved are given a semiclassical
interpretation by extending the billiard boundaries to complex space and
generalizing specular reflection to complex rays. We give analytical
expressions for the splittings, and show that the dominant contributions come
from {\em chaos-assisted}\/ paths that tunnel into and out of the chaotic
layer.Comment: 4 pages, uuencoded postscript file, replaces a corrupted versio
Monte--Carlo Thermodynamic Bethe Ansatz
We introduce a Monte--Carlo simulation approach to thermodynamic Bethe ansatz
(TBA). We exemplify the method on one particle integrable models, which include
a free boson and a free fermions systems along with the scaling Lee--Yang model
(SLYM). It is confirmed that the central charges and energies are correct to a
very good precision, typically 0.1% or so. The advantage of the method is that
it enables the calculation of all the dimensions and even the particular
partition function.Comment: 22 pages. Added a footnote and realizations for the minimal models.
Fortran program, mont-s.f90, available from the source lin
I ask the profession to stand still: The Evolution of American public accountancy, 1927-1962
This paper traces the emergence of the AICPA as an effective national representative of the American profession. Central to this evolution was a broadening of the Institute\u27s outlook to encompass all practicing CPAs and to embrace the benefits of public relations and lobbying. The paper begins with the Wall Street elite that dominated the Institute\u27s predecessor, the AIA, and describes the pressures for reform that culminated in the Securities Acts of 1933 and 1934 and set this evolution in motion. The final section makes use of former AICPA president Marquis Eaton\u27s papers to show how pressure from the Securities and Exchange Commission, from competing professions, and from a geometric increase in the profession\u27s numbers brought a more pragmatic and aggresive leadership to the Institute, one that more closely resembles the modern AICPA
Near zero modes in condensate phases of the Dirac theory on the honeycomb lattice
We investigate a number of fermionic condensate phases on the honeycomb
lattice, to determine whether topological defects (vortices and edges) in these
phases can support bound states with zero energy. We argue that topological
zero modes bound to vortices and at edges are not only connected, but should in
fact be \emph{identified}. Recently, it has been shown that the simplest s-wave
superconducting state for the Dirac fermion approximation of the honeycomb
lattice at precisely half filling, supports zero modes inside the cores of
vortices (P. Ghaemi and F. Wilczek, 2007). We find that within the continuum
Dirac theory the zero modes are not unique neither to this phase, nor to half
filling. In addition, we find the \emph{exact} wavefunctions for vortex bound
zero modes, as well as the complete edge state spectrum of the phases we
discuss. The zero modes in all the phases we examine have even-numbered
degeneracy, and as such pairs of any Majorana modes are simply equivalent to
one ordinary fermion. As a result, contrary to bound state zero modes in superconductors, vortices here do \emph{not} exhibit non-Abelian exchange
statistics. The zero modes in the pure Dirac theory are seemingly topologically
protected by the effective low energy symmetry of the theory, yet on the
original honeycomb lattice model these zero modes are split, by explicit
breaking of the effective low energy symmetry.Comment: Final version including numerics, accepted for publication in PR
Mass and Gas Profiles in A1689: Joint X-ray and Lensing Analysis
We carry out a comprehensive joint analysis of high quality HST/ACS and
Chandra measurements of A1689, from which we derive mass, temperature, X-ray
emission and abundance profiles. The X-ray emission is smooth and symmetric,
and the lensing mass is centrally concentrated indicating a relaxed cluster.
Assuming hydrostatic equilibrium we deduce a 3D mass profile that agrees
simultaneously with both the lensing and X-ray measurements. However, the
projected temperature profile predicted with this 3D mass profile exceeds the
observed temperature by ~30% at all radii, a level of discrepancy comparable to
the level found for other relaxed clusters. This result may support recent
suggestions from hydrodynamical simulations that denser, more X-ray luminous
small-scale structure can bias observed temperature measurements downward at
about the same (~30%) level. We determine the gas entropy at 0.1r_{vir} (where
r_{vir} is the virial radius) to be ~800 keV cm^2, as expected for a high
temperature cluster, but its profile at >0.1r_{vir} has a power-law form with
index ~0.8, considerably shallower than the ~1.1 index advocated by theoretical
studies and simulations. Moreover, if a constant entropy ''floor'' exists at
all, then it is within a small region in the inner core, r<0.02r_{vir}, in
accord with previous theoretical studies of massive clusters.Comment: 18 pages, 20 figures, 7 tables, accepted for publication in MNRAS,
minor changes to match published versio
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