7,404 research outputs found
Infinite matrix product states, Conformal Field Theory and the Haldane-Shastry model
We generalize the Matrix Product States method using the chiral vertex
operators of Conformal Field Theory and apply it to study the ground states of
the XXZ spin chain, the J1-J2 model and random Heisenberg models. We compute
the overlap with the exact wave functions, spin-spin correlators and the Renyi
entropy, showing that critical systems can be described by this method. For
rotational invariant ansatzs we construct an inhomogenous extension of the
Haldane-Shastry model with long range exchange interactions.Comment: 5 pages, 4 figures, 1 reference adde
Double barred galaxies at intermediate redshifts: A feasibility study
Despite the increasing number of studies of barred galaxies at intermediate
and high redshifts, double-barred (S2B) systems have only been identified in
the nearby (z<0.04) universe thus far. In this feasibility study we demonstrate
that the detection and analysis of S2Bs is possible at intermediate redshifts
(0.1 < z < 0.5) with the exquisite resolution of the Hubble Space Telescope
Advanced Camera for Surveys (HST/ACS). We identify barred galaxies in the
HST/ACS data of the Great Observatories Origins Deep Survey (GOODS) using a
novel method. The radial profile of the Gini coefficient -- a model-independent
structure parameter -- is able to detect bars in early-type galaxies that are
large enough that they might host an inner bar of sufficient angular size.
Using this method and subsequent examination with unsharp masks and ellipse
fits we identified the two most distant S2Bs currently known (at redshifts
z=0.103 and z=0.148). We investigate the underlying stellar populations of
these two galaxies through a detailed colour analysis, in order to demonstrate
the analysis that could be performed on a future sample of
intermediate-redshift S2Bs. We also identify two S2Bs and five S2B candidates
in the HST/ACS data of the Cosmic Evolution Survey (COSMOS). Our detections of
distant S2Bs show that deep surveys like GOODS and COSMOS have the potential to
push the limit for S2B detection and analysis out by a factor of ten in
redshift and lookback time (z=0.5, t=5Gyr) compared to the previously known
S2Bs. This in turn would provide new insight into the formation of these
objects.Comment: 9 pages + 10 figures. Accepted for publication in MNRAS. Main change
from version 1 is an extension of the introduction/motivation and discussion
section. A full resolution version including colour figures is available at
http://www.astro.unibas.ch/~tlisker/papers/lisker2006_s2b.pd
An exact formalism to study the thermodynamic properties of hard-sphere systems under spherical confinement
This paper presents a modified grand canonical ensemble which provides a new
simple and efficient scheme to study few-body fluid-like inhomogeneous systems
under confinement. The new formalism is implemented to investigate the exact
thermodynamic properties of a hard sphere (HS) fluid-like system with up to
three particles confined in a spherical cavity. In addition, the partition
function of this system was used to analyze the surface thermodynamic
properties of the many-HS system and to derive the exact curvature dependence
of both the surface tension and adsorption in powers of the density. The
expressions for the surface tension and the adsorption were also obtained for
the many- HS system outside of a fixed hard spherical object. We used these
results to derive the dependence of the fluid-substrate Tolman length up to
first order in density.Comment: 6 figures. The paper includes new exact results about hard spheres
fluid-like system
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