5,310 research outputs found
Superspace formulation of general massive gauge theories and geometric interpretation of mass-dependent BRST symmetries
A superspace formulation is proposed for the osp(1,2)-covariant Lagrangian
quantization of general massive gauge theories. The superalgebra os0(1,2) is
considered as subalgebra of sl(1,2); the latter may be considered as the
algebra of generators of the conformal group in a superspace with two
anticommuting coordinates. The mass-dependent (anti)BRST symmetries of proper
solutions of the quantum master equations in the osp(1,2)-covariant formalism
are realized in that superspace as invariance under translations combined with
mass-dependent special conformal transformations. The Sp(2) symmetry - in
particular the ghost number conservation - and the "new ghost number"
conservation are realized as invariance under symplectic rotations and
dilatations, respectively. The transformations of the gauge fields - and of the
full set of necessarily required (anti)ghost and auxiliary fields - under the
superalgebra sl(1,2) are determined both for irreducible and first-stage
reducible theories with closed gauge algebra.Comment: 35 pages, AMSTEX, precision of reference
Observing the very low-surface brightness dwarfs in a deep field in the VIRGO cluster: constraints on Dark Matter scenarios
We report the discovery of 11 very faint (r< 23), low surface brightness
({\mu}_r< 27 mag/arcsec^2) dwarf galaxies in one deep field in the Virgo
cluster, obtained by the prime focus cameras (LBC) at the Large Binocular
Telescope (LBT). These extend our previous sample to reach a total number of 27
galaxies in a field of just of 0.17 deg^2 located at a median distance of 390
kpc from the cluster center. Their association with the Virgo cluster is
supported by their separate position in the central surface brightness - total
magnitude plane with respect to the background galaxies of similar total
magnitude. For a significant fraction (26\%) of the sample the association to
the cluster is confirmed by spectroscopic follow-up. We show that the mere
abundance of satellite galaxies corresponding to our observed number in the
target field provides extremely tight constraints on Dark Matter models with
suppressed power spectrum compared to the Cold Dark Matter case, independently
of the galaxy luminosity distribution. In particular, requiring the observed
number of satellite galaxies not to exceed the predicted abundance of Dark
Matter sub-halos yields a limit m_X >3 keV at 1-{\sigma} and m_X > 2.3 keV at
2-{\sigma} confidence level for the mass of thermal Warm Dark Matter particles.
Such a limit is competitive with other limits set by the abundance of
ultra-faint satellite galaxies in the Milky Way, is completely independent of
baryon physics involved in galaxy formation, and has the potentiality for
appreciable improvements with next observations. We extend our analysis to Dark
Matter models based on sterile neutrinos, showing that our observations set
tight constraints on the combination of sterile neutrino mass m_{\nu} and
mixing parameter sin^2(2{\theta}). We discuss the robustness of our results
with respect to systematics.Comment: Accepted for publication in Astronomy & Astrophysic
Versatile Cold Atom Source for Multi-Species Experiments
We present a dual-species oven and Zeeman slower setup capable of producing
slow, high-flux atomic beams for loading magneto-optical traps. Our compact and
versatile system is based on electronic switching between different magnetic
field profiles and is applicable to a wide range of multi-species experiments.
We give details of the vacuum setup, coils and simple electronic circuitry. In
addition, we demonstrate the performance of our system by optimized, sequential
loading of magneto-optical traps of lithium-6 and cesium-133.Comment: 7 pages, 10 figure
The detection of ultra-faint low surface brightness dwarf galaxies in the Virgo Cluster: a Probe of Dark Matter and Baryonic Physics
We have discovered 11 ultra-faint () low surface brightness
(LSB, central surface brightness ) dwarf galaxy
candidates in one deep Virgo field of just arcmin obtained by the
Large Binocular Camera (LBC) at the Large Binocular Telescope (LBT). Their
association with the Virgo cluster is supported by their distinct position in
the central surface brightness - total magnitude plane with respect to the
background galaxies of similar total magnitude. They have typical absolute
magnitudes and scale sizes, if at the distance of Virgo, in the range
and pc,
respectively. Their colors are consistent with a gradually declining star
formation history with a specific star formation rate of the order of
yr, i.e. 10 times lower than that of main sequence star
forming galaxies. They are older than the cluster formation age and appear
regular in morphology. They represent the faintest extremes of the population
of low luminosity LSB dwarfs that has been recently detected in wider surveys
of the Virgo cluster. Thanks to the depth of our observations we are able to
extend the Virgo luminosity function down to (corresponding to
total masses M), finding an average faint-end slope
. This relatively steep slope puts interesting constraints
on the nature of the Dark Matter and in particular on warm Dark Matter (WDM)
often invoked to solve the overprediction of the dwarf number density by the
standard CDM scenario. We derive a lower limit on the WDM particle mass
keV.Comment: accepted for publication in ApJ, 13 pages, 6 figure
High efficiency tomographic reconstruction of quantum states by quantum nondemolition measurements
We propose a high efficiency tomographic scheme to reconstruct an unknown
quantum state of the qubits by using a series of quantum nondemolition (QND)
measurements. The proposed QND measurements of the qubits are implemented by
probing the the stationary transmissions of the dispersively-coupled resonator.
It is shown that only one kind of QND measurements is sufficient to determine
all the diagonal elements of the density matrix of the detected quantum state.
The remaining non-diagonal elements of the density matrix can be determined by
other spectral measurements by beforehand transferring them to the diagonal
locations using a series of unitary operations. Compared with the pervious
tomographic reconstructions based on the usual destructively projective (DP)
measurements (wherein one kind of such measurements could only determine one
diagonal element of the density matrix), the present approach exhibits
significantly high efficiency for N-qubit (N > 1). Specifically, our generic
proposal is demonstrated by the experimental circuit-quantumelectrodynamics
(circuit-QED) systems with a few Josephson charge qubits.Comment: 9pages,4figure
Estimating precipitation on early Mars using a radiative-convective model of the atmosphere and comparison with inferred runoff from geomorphology
We compare estimates of atmospheric precipitation during the Martian
Noachian-Hesperian boundary 3.8 Gyr ago as calculated in a radiative-convective
column model of the atmosphere with runoff values estimated from a
geomorphological analysis of dendritic valley network discharge rates. In the
atmospheric model, we assume CO2-H2O-N2 atmospheres with surface pressures
varying from 20 mb to 3 bar with input solar luminosity reduced to 75% the
modern value.
Results from the valley network analysis are of the order of a few mm d-1
liquid water precipitation (1.5-10.6 mm d-1, with a median of 3.1 mm d-1).
Atmospheric model results are much lower, from about 0.001-1 mm d-1 of snowfall
(depending on CO2 partial pressure). Hence, the atmospheric model predicts a
significantly lower amount of precipitated water than estimated from the
geomorphological analysis. Furthermore, global mean surface temperatures are
below freezing, i.e. runoff is most likely not directly linked to
precipitation. Therefore, our results strongly favor a cold early Mars with
episodic snowmelt as a source for runoff.
Our approach is challenged by mostly unconstrained parameters, e.g.
greenhouse gas abundance, global meteorology (for example, clouds) and
planetary parameters such as obliquity- which affect the atmospheric result -
as as well as by inherent problems in estimating discharge and runoff on
ancient Mars, such as a lack of knowledge on infiltration and evaporation rates
and on flooding timescales, which affect the geomorphological data.
Nevertheless, our work represents a first step in combining and interpreting
quantitative tools applied in early Mars atmospheric and geomorphological
studies.Comment: accepted in Planetary and Space Science, 37 pages, 14 figures, 2
table
The derived category of surface algebras: the case of the torus with one boundary component
In this paper we refine the main result of a previous paper of the author
with Grimeland on derived invariants of surface algebras. We restrict to the
case where the surface is a torus with one boundary component and give an
easily computable derived invariant for such surface algebras. This result
permits to give answers to open questions on gentle algebras: it provides
examples of gentle algebras with the same AG-invariant (in the sense of
Avella-Alaminos and Geiss) that are not derived equivalent and gives a partial
positive answer to a conjecture due to Bobi\'nski and Malicki on gentle
-cycles algebras.Comment: 22 pages, a mistake concerning the computation of the mapping class
group has been fixed, version 3: 25 pages, to appear in Algebras and
Representation Theor
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