40 research outputs found
Symplectic gaugings and the field-antifield formalism
We give an example of how conventional gauging methods obstruct a systematic
analysis of gauged supergravities. We discuss how the embedding tensor
formalism deals with these problems and argue that the gauge algebra related to
the embedding tensor formalism is soft, open and reducible. We connect the
embedding tensor formalism to the field-antifield (or Batalin-Vilkovisky)
formalism, which is the most general formulation known for gauge theories.Comment: Contribution to the Proceedings of the XVIth European Workshop on
String Theory in Madrid (June 14-18, 2010), 10 page
Generalized gaugings and the field-antifield formalism
We discuss the algebra of general gauge theories that are described by the
embedding tensor formalism. We compare the gauge transformations dependent and
independent of an invariant action, and argue that the generic transformations
lead to an infinitely reducible algebra. We connect the embedding tensor
formalism to the field-antifield (or Batalin-Vilkovisky) formalism, which is
the most general formulation known for general gauge theories and their
quantization. The structure equations of the embedding tensor formalism are
included in the master equation of the field-antifield formalism.Comment: 42 pages; v2: some clarifications and 1 reference added; version to
be published in JHE
An Optical Velocity for the Phoenix Dwarf Galaxy
We present the results of a VLT observing program carried out in service mode
using FORS1 on ANTU in Long Slit mode to determine the optical velocities of
nearby low surface brightness galaxies. As part of our program of service
observations we obtained long-slit spectra of several members of the Phoenix
dwarf galaxy from which we derive an optical helio-centric radial velocity of
-13 +/- 9km/s. This agrees very well with the velocity of the most promising of
the HI clouds seen around Phoenix, which has a helio-centric velocity of -23
km/s, but is significantly different to the recently published optical
heliocentric velocity of Phoenix of -52 +/- 6 km/s of Gallart et al. (2001).Comment: Aceepted for publication in MNRA
Electric/magnetic duality for chiral gauge theories with anomaly cancellation
We show that 4D gauge theories with Green-Schwarz anomaly cancellation and
possible generalized Chern-Simons terms admit a formulation that is manifestly
covariant with respect to electric/magnetic duality transformations. This
generalizes previous work on the symplectically covariant formulation of
anomaly-free gauge theories as they typically occur in extended supergravity,
and now also includes general theories with (pseudo-)anomalous gauge
interactions as they may occur in global or local N=1 supersymmetry. This
generalization is achieved by relaxing the linear constraint on the embedding
tensor so as to allow for a symmetric 3-tensor related to electric and/or
magnetic quantum anomalies in these theories. Apart from electric and magnetic
gauge fields, the resulting Lagrangians also feature two-form fields and can
accommodate various unusual duality frames as they often appear, e.g., in
string compactifications with background fluxes.Comment: 37 pages; v2: typos corrected and 1 reference adde
Symplectic structure of N=1 supergravity with anomalies and Chern-Simons terms
The general actions of matter-coupled N=1 supergravity have Peccei-Quinn
terms that may violate gauge and supersymmetry invariance. In addition, N=1
supergravity with vector multiplets may also contain generalized Chern-Simons
terms. These have often been neglected in the literature despite their
importance for gauge and supersymmetry invariance. We clarify the interplay of
Peccei-Quinn terms, generalized Chern-Simons terms and quantum anomalies in the
context of N=1 supergravity and exhibit conditions that have to be satisfied
for their mutual consistency. This extension of the previously known N=1
matter-coupled supergravity actions follows naturally from the embedding of the
gauge group into the group of symplectic duality transformations. Our results
regarding this extension provide the supersymmetric framework for studies of
string compactifications with axionic shift symmetries, generalized
Chern-Simons terms and quantum anomalies.Comment: 27 pages; v2: typos corrected; version to be published in
Class.Quantum Gra
The Search for High-Mass X-ray Binaries in the Phoenix Dwarf Galaxy
We report on the first X-ray images of the Phoenix dwarf galaxy, taken with
\emph{XMM-Newton} in July 2009. This local group dwarf galaxy shares
similarities with the Small Magellanic Cloud (SMC) including a burst of star
formation 50 Myr ago. The SMC has an abundance of High Mass X-ray
Binaries (HMXBs) and so we have investigated the possibility of an HMXB
population in Phoenix with the intention of furthering the understanding of the
HMXB-star formation rate relation. The data from the combined European Photon
Imaging Cameras (EPIC) were used to distinguish between different source
classes (foreground stars, background galaxies, AGN and supernova remnants)
using EPIC hardness ratios and correlations with optical and radio catalogues.
Of the 81 X-ray sources in the field of view, six are foreground stars, four
are galaxies and one is an AGN. The remaining sources with optical counterparts
have log() consistent with AGN in the local universe.
Further investigation of five sources in the field of view suggests they are
all background AGN. Their position behind the gas cloud associated with Phoenix
makes them a possible tool for further probing the metallicity of this region.
We find no evidence for any HMXBs in Phoenix at this time. This rules out the
existence of the X-ray persistent supergiant X-ray binary systems. However the
transient nature of the Be/X-ray binaries means we cannot rule out a population
of these sources but can conclude that it is not extensive.Comment: 13 pages, 4 figures, 4 tables, Accepted for publication in MNRA
Lectures on Gauged Supergravity and Flux Compactifications
The low-energy effective theories describing string compactifications in the
presence of fluxes are so-called gauged supergravities: deformations of the
standard abelian supergravity theories. The deformation parameters can be
identified with the various possible (geometric and non-geometric) flux
components. In these lecture notes we review the construction of gauged
supergravities in a manifestly duality covariant way and illustrate the
construction in several examples.Comment: 48 pages, lectures given at the RTN Winter School on Strings,
Supergravity and Gauge Theories, CERN, January 200
A wide-area view of the Phoenix dwarf galaxy from VLT/FORS imaging
We present results from a wide-area photometric survey of the Phoenix dwarf
galaxy, one of the rare dwarf irregular/ dwarf spheroidal transition type
galaxies (dTs) of the Local Group (LG). These objects offer the opportunity to
study the existence of possible evolutionary links between the late- and early-
type LG dwarf galaxies, since the properties of dTs suggest that they may be
dwarf irregulars in the process of transforming into dwarf spheroidals. Using
FORS at the VLT we have acquired VI photometry of Phoenix. The data reach a
S/N~10 just below the horizontal branch of the system and consist of a mosaic
of images that covers an area of 26' x 26' centered on the coordinates of the
optical center of the galaxy. Examination of the colour-magnitude diagram and
luminosity function revealed the presence of a bump above the red clump,
consistent with being a red giant branch bump. The deep photometry combined
with the large area covered allows us to put on a secure ground the
determination of the overall structural properties of the galaxy and to derive
the spatial distribution of stars in different evolutionary phases and age
ranges, from 0.1 Gyr to the oldest stars. The best-fitting profile to the
overall stellar population is a Sersic profile of Sersic radius R_S =
1.82'+-0.06' and m=0.83+-0.03. We confirm that the spatial distribution of
stars is found to become more and more centrally concentrated the younger the
stellar population, as reported in previous studies. This is similar to the
stellar population gradients found for close-by Milky Way dwarf spheroidal
galaxies. We quantify such spatial variations by analyzing the surface number
density profiles of stellar populations in different age ranges; [Abridged]Comment: 21 pages; 11 figures. Accepted for publication in MNRA
VLT/FORS1 spectrophotometry of the first planetary nebula discovered in the Phoenix dwarf galaxy
Context: A planetary nebula (PN) candidate was discovered during FORS imaging of the Local Group dwarf galaxy Phoenix.
Aims: We use this PN to complement abundances from red-giant stars.
Methods: FORS spectroscopy was used to confirm the PN classification. Empirical methods and photoionization modeling were used to derive elemental abundances from the emission line fluxes and to characterize the central star.
Results: For the elements deemed most reliable for measuring the metallicity of the interstellar medium (ISM) from which the PN formed, [O/H] ⌠â0.46 and [Ar/H] ⌠â1.03. [O/H] has lower measurement errors but greater uncertainties due to the unresolved issue of oxygen enrichment in the PN precursor star.
Conclusions: Earlier than 2 Gyr ago (the lower limit of the derived age for the central star) the ISM had Z = 0.002â0.008, a range slightly more metal-rich than the one provided by stars. Comparing our PN-to-stellar values to surveys of other dwarf Local Group galaxies, Phoenix appears to be an outlier