219 research outputs found
The Gribov parameter and the dimension two gluon condensate in Euclidean Yang-Mills theories in the Landau gauge
The local composite operator A^2 is added to the Zwanziger action, which
implements the restriction to the Gribov region in Euclidean Yang-Mills
theories in the Landau gauge. We prove the renormalizability of this action to
all orders of perturbation theory. This allows to study the dimension two gluon
condensate by the local composite operator formalism when the restriction
is taken into account. The effective action is evaluated at one-loop order in
the MSbar scheme. We obtain explicit values for the Gribov parameter and for
the mass parameter due to , but the expansion parameter turns out to be
rather large. Furthermore, an optimization of the perturbative expansion in
order to reduce the dependence on the renormalization scheme is performed. The
properties of the vacuum energy, with or without , are investigated. It is
shown that in the original Gribov-Zwanziger formulation (without ), the
vacuum energy is always positive at 1-loop order, independently from the
renormalization scheme and scale. With , we are unable to come to a
definite conclusion at the order considered. In the MSbar scheme, we still find
a positive vacuum energy, again with a relatively large expansion parameter,
but there are renormalization schemes in which the vacuum energy is negative,
albeit the dependence on the scheme itself appears to be strong. We recover the
well known consequences of the restriction, and this in the presence of :
an infrared suppression of the gluon propagator and an enhancement of the ghost
propagator. This behaviour is in qualitative agreement with the results
obtained from the studies of the Schwinger-Dyson equations and from lattice
simulations.Comment: 42 pages, 10 .eps figures. v2: Version accepted for publication in
Phys.Rev.D. Added references. Technical details have been collected in two
appendice
Estudo do gênero Lentaria corner (Fungi, Basidiomycota) na Unidade de Conservação Ambiental Desterro, Florianópolis, Santa Catarina, Brasil
TCC(graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Biológicas. Biologia.O gênero Lentaria é composto por fungos com basidiomas ramificados de coloração bege a marrom, apresentando hifas generativas de parede levemente espessada e basidiósporos hialinos, lisos, suboblongos a lacrimoides. Este é o primeiro estudo desenvolvido acerca do gênero para o Brasil e visa ampliar o conhecimento da diversidade do gênero. Este estudo sobre Lentaria realizado na Unidade de Conservação Ambiental Desterro (UCAD) resultou na coleta de nove espécimes de Lentaria e na identificação de cinco táxons, sendo eles: Lentaria surculus, L. byssiseda, L. micheneri, Lentaria sp1 e Lentaria sp2. Todas as espécies constituem novas citações para a UCAD e Florianópolis, com L. byssiseda e L. micheneri novas citações para o Brasil. Neste trabalho, além das descrições dos espécimes, são apresentados uma chave de identificação dos táxons, fotografias dos basidiomas e ilustrações das microestruturas são apresentados
Quantum graphs as holonomic constraints
We consider the dynamics on a quantum graph as the limit of the dynamics
generated by a one-particle Hamiltonian in R^2 with a potential having a deep
strict minimum on the graph, when the width of the well shrinks to zero. For a
generic graph we prove convergence outside the vertices to the free dynamics on
the edges. For a simple model of a graph with two edges and one vertex, we
prove convergence of the dynamics to the one generated by the Laplacian with
Dirichlet boundary conditions in the vertex.Comment: 28 pages, 3 figure
A time-dependent perturbative analysis for a quantum particle in a cloud chamber
We consider a simple model of a cloud chamber consisting of a test particle
(the alpha-particle) interacting with two other particles (the atoms of the
vapour) subject to attractive potentials centered in . At time zero the alpha-particle is described by an outgoing
spherical wave centered in the origin and the atoms are in their ground state.
We show that, under suitable assumptions on the physical parameters of the
system and up to second order in perturbation theory, the probability that both
atoms are ionized is negligible unless lies on the line joining the
origin with . The work is a fully time-dependent version of the original
analysis proposed by Mott in 1929.Comment: 23 page
Wide-field weak lensing by RXJ1347-1145
We present an analysis of weak lensing observations for RXJ1347-1145 over a
43' X 43' field taken in B and R filters on the Blanco 4m telescope at CTIO.
RXJ1347-1145 is a massive cluster at redshift z=0.45. Using a population of
galaxies with 20<R<26, we detect a weak lensing signal at the p<0.0005 level,
finding best-fit parameters of \sigma_v=1400^{+130}_{-140} km s^{-1} for a
singular isothermal sphere model and r_{200} = 3.5^{+0.8}_{-0.2} Mpc with c =
15^{+64}_{-10} for a NFW model in an \Omega_m = 0.3, \Omega_\Lambda = 0.7
cosmology. In addition, a mass to light ratio M/L_R =90 \pm 20 M_\odot /
L_{R\odot} was determined. These values are consistent with the previous weak
lensing study of RXJ1347--1145 by Fischer and Tyson, 1997, giving strong
evidence that systemic bias was not introduced by the relatively small field of
view in that study. Our best-fit parameter values are also consistent with
recent X-ray studies by Allen et al, 2002 and Ettori et al, 2001, but are not
consistent with recent optical velocity dispersion measurements by Cohen and
Kneib, 2002.Comment: accepted to ApJ, tentative publication 10 May 2005, v624
Ionization for Three Dimensional Time-dependent Point Interactions
We study the time evolution of a three dimensional quantum particle under the
action of a time-dependent point interaction fixed at the origin. We assume
that the ``strength'' of the interaction (\alpha(t)) is a periodic function
with an arbitrary mean. Under very weak conditions on the Fourier coefficients
of (\alpha(t)), we prove that there is complete ionization as (t \to \infty),
starting from a bound state at time (t = 0). Moreover we prove also that, under
the same conditions, all the states of the system are scattering states.Comment: Some improvements and some references added, 26 pages, LaTe
Probing the Relation Between X-ray-Derived and Weak-Lensing-Derived Masses for Shear-Selected Galaxy Clusters: I. A781
We compare X-ray and weak-lensing masses for four galaxy clusters that
comprise the top-ranked shear-selected cluster system in the Deep Lens Survey.
The weak-lensing observations of this system, which is associated with A781,
are from the Kitt Peak Mayall 4-m telescope, and the X-ray observations are
from both Chandra and XMM-Newton. For a faithful comparison of masses, we adopt
the same matter density profile for each method, which we choose to be an NFW
profile. Since neither the X-ray nor weak-lensing data are deep enough to well
constrain both the NFW scale radius and central density, we estimate the scale
radius using a fitting function for the concentration derived from cosmological
hydrodynamic simulations and an X-ray estimate of the mass assuming
isothermality. We keep this scale radius in common for both X-ray and
weak-lensing profiles, and fit for the central density, which scales linearly
with mass. We find that for three of these clusters, there is agreement between
X-ray and weak-lensing NFW central densities, and thus masses. For the other
cluster, the X-ray central density is higher than that from weak-lensing by 2
sigma. X-ray images suggest that this cluster may be undergoing a merger with a
smaller cluster. This work serves as an additional step towards understanding
the possible biases in X-ray and weak-lensing cluster mass estimation methods.
Such understanding is vital to efforts to constrain cosmology using X-ray or
weak-lensing cluster surveys to trace the growth of structure over cosmic time.Comment: 14 pages, 7 figures, matches version in Ap
Discovery of a Galaxy Cluster via Weak Lensing
We report the discovery of a cluster of galaxies via its weak gravitational
lensing effect on background galaxies, the first spectroscopically confirmed
cluster to be discovered through its gravitational effects rather than by its
electromagnetic radiation. This fundamentally different selection mechanism
promises to yield mass-selected, rather than baryon or photon-selected, samples
of these important cosmological probes. We have confirmed this cluster with
spectroscopic redshifts of fifteen members at z=0.276, with a velocity
dispersion of 615 km/s. We use the tangential shear as a function of source
photometric redshift to estimate the lens redshift independently and find z_l =
0.30 +- 0.08. The good agreement with the spectroscopy indicates that the
redshift evolution of the mass function may be measurable from the imaging data
alone in shear-selected surveys.Comment: revised version with minor changes, to appear in ApJ
The Landau gauge gluon and ghost propagator in the refined Gribov-Zwanziger framework in 3 dimensions
In previous works, we have constructed a refined version of the
Gribov-Zwanziger action in 4 dimensions, by taking into account a novel
dynamical effect. In this paper, we explore the 3-dimensional case. Analogously
as in 4 dimensions, we obtain a ghost propagator behaving like in the
infrared, while the gluon propagator reaches a finite nonvanishing value at
zero momentum. Simultaneously, a clear violation of positivity by the gluon
propagator is also found. This behaviour of the propagators turns out be in
agreement with the recent numerical simulations.Comment: 26 pages, 16 .eps figures. v3: version accepted for publication in
Phys Rev
Multiple Weak Deflections in Galaxy-Galaxy Lensing
The frequency and effects of multiple weak deflections in galaxy-galaxy
lensing are investigated via Monte Carlo simulations. The lenses in the
simulations are galaxies with known redshifts and known rest-frame blue
luminosities. The frequency of multiple deflections above a given threshold
shear value is quantified for discrete source redshifts, as well as for a set
of sources that are broadly distributed in redshift space. In general, the
closest lens in projection on the sky is not the only lens for a given source.
In addition, ~50% of the time the closest lens is not the most important lens
for a given source. Compared to a naive single-deflection calculation in which
only the lensing due to the closest weak lens is considered, a full
multiple-deflection calculation yields a higher net shear for individual
sources, as well as a higher mean tangential shear around the lens centers. The
full multiple-deflection calculation also shows that galaxy-galaxy lensing may
contribute a substantial amount to cosmic shear on small angular scales. The
degree to which galaxy-galaxy lensing contributes to the small-scale cosmic
shear is, however, quite sensitive to the mass adopted for the halos of L_B*
galaxies. Changing the halo mass by a factor of ~2.5 changes the contribution
of galaxy-galaxy lensing to the cosmic shear by a factor of ~3 on scales of
order 1 arcmin. The contribution of galaxy-galaxy lensing to cosmic shear
decreases rapidly with angular scale and extrapolates to zero at scales of
order 5 arcmin. This last result is roughly independent of the halo mass and
suggests that for scales greater than about 5 arcmin, cosmic shear is
insensitive to the details of the gravitational potentials of large galaxies.Comment: accepted for publication in ApJ; 35 pages, 15 figures; full text with
high-resolution Figure 1 available at
http://firedrake.bu.edu/preprints/preprints.htm
- …