51,165 research outputs found
Using zeros of the canonical partition function map to detect signatures of a Berezinskii-Kosterlitz-Thouless transition
Using the two dimensional model as a test case, we show that
analysis of the Fisher zeros of the canonical partition function can provide
signatures of a transition in the Berezinskii-Kosterlitz-Thouless ()
universality class. Studying the internal border of zeros in the complex
temperature plane, we found a scenario in complete agreement with theoretical
expectations which allow one to uniquely classify a phase transition as in the
class of universality. We obtain in excellent accordance with
previous results. A careful analysis of the behavior of the zeros for both
regions and in the
thermodynamic limit show that goes to zero in the former
case and is finite in the last one
Mass, angular-momentum, and charge inequalities for axisymmetric initial data
We present the key elements of the proof of an upper bound for
angular-momentum and charge in terms of the mass for electro-vacuum
asymptotically flat axisymmetric initial data sets with simply connected orbit
space
Coleman meets Schwinger
It is well known that spherical D-branes are nucleated in the presence of an
external RR electric field. Using the description of D-branes as solitons of
the tachyon field on non-BPS D-branes, we show that the brane nucleation
process can be seen as the decay of the tachyon false vacuum. This process can
describe the decay of flux-branes in string theory or the decay of quintessence
potentials arising in flux compactifications.Comment: 5 pages, 2 figure
Probing Mass Segregation in NGC 6397
In this study, we present a detailed study of mass segregation in the
globular clister NGC 6397. First, we carry out a photometric analysis of
projected ESO-VLT data (between 1 and 10 arcmin from the cluster centre),
presenting the luminosity function corrected by completeness. The luminosity
function shows a higher density of bright stars near the central region of the
data, with respect to the outer region. We calculate a deprojected model
(covering the whole cluster) estimating a total number of stars of 193000 +-
19000. The shapes of the surface brightness and density-number profiles versus
the radial coordinate r (instead of the projected coordinate R) lead to a
decreasing luminosity for an average star, and thus of mass, up to 1 arcmin,
quantifying the mass segregation. The deprojected model does not show evidence
of mass segregation outside this region
The Power Spectrum of Galaxies in the Nearby Universe
We compute the power spectrum of galaxy density fluctuations in a recently
completed redshift survey of optically-selected galaxies in the southern
hemisphere (SSRS2). The amplitude and shape of the SSRS2 power spectrum are
consistent with results of the Center for Astrophysics redshift survey of the
northern hemisphere (CfA2), including the abrupt change of slope on a scale of
30-50Mpc/h; these results are reproducible for independent volumes of space and
variations are consistent with the errors estimated from mock surveys. Taken
together, the SSRS2 and CfA2 form a complete sample of 14,383 galaxies which
covers one-third of the sky. The power spectrum of this larger sample continues
to rise on scales up to ~ 200Mpc/h, with weak evidence for flattening on the
largest scales. The SSRS2+CfA2 power spectrum and the power spectrum
constraints implied by COBE are well-matched by an Omega*h ~ 0.2,
Omega+lambda_0=1 CDM model with minimal biasing of optically-selected galaxies.Comment: Accepted for publication in The Astrophysical Journal Letters, Sept.
23, 1994. 10 pages uuencoded compressed postscript, including two figures.
JHU-9410200
Gauge fields in a string-cigar braneworld
In this work we investigate the properties of an Abelian gauge vector field
in a thin and in a smoothed string-like braneworld, the so-called string-cigar
model. This thick brane scenario satisfies the regularity conditions and it can
be regarded as an interior and exterior string-like solution. The source
undergoes a geometric Ricci flow which is connected to a variation of the bulk
cosmological constant. The Ricci flow changes the width and amplitude of the
massless mode at the brane core and recover the usual thin string-like behavior
at large distances. By numerical means we obtain the Kaluza-Klein (KK) spectrum
for both the thin brane and the string-cigar. It turns out that both models
exhibit a mass gap between the massless and the massive modes and between the
high and the low mass regimes. The KK modes are smooth near the brane and their
amplitude are enhanced by the string-cigar core. The analogue Schr\"odinger
potential is also tuned by the geometric flow.Comment: The discussion about the Kaluza-Klein spectrum of the gauge field was
improved. Numerical analysis was adapted to the conventional notation on
Kaluza-Klein number. Some graphics were modified for considering other
notation. Results unchanged. References added. Corrected typos. 17 pages. 6
figures. To match version to appears in Physics Letters
Matrix factorizations for quantum complete intersections
We introduce twisted matrix factorizations for quantum complete intersections
of codimension two. For such an algebra, we show that in a given dimension,
almost all the indecomposable modules with bounded minimal projective
resolutions correspond to such matrix factorizations.Comment: 13 page
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