10,288 research outputs found
Topological Extensions of Noether Charge Algebras carried by D-p-branes
We derive the fully extended supersymmetry algebra carried by D-branes in a
massless type IIA superspace vacuum. We find that the extended algebra contains
not only topological charges that probe the presence of compact spacetime
dimensions but also pieces that measure non-trivial configurations of the gauge
field on the worldvolume of the brane. Furthermore there are terms that measure
the coupling of the non-triviality of the worldvolume regarded as a U(1)-bundle
of the gauge field to possible compact spacetime dimensions. In particular, the
extended algebra carried by the D-2-brane can contain the charge of a Dirac
monopole of the gauge field. In the course of this work we derive a set of
generalized Gamma-matrix identities that include the ones presently known for
the IIA case.
In the first part of the paper we give an introduction to the basic notions
of Noether current algebras and charge algebras; furthermore we find a Theorem
that describes in a general context how the presence of a gauge field on the
worldvolume of an embedded object transforming under the symmetry group on the
target space alters the algebra of the Noether charges, which otherwise would
be the same as the algebra of the symmetry group. This is a phenomenon recently
found by Sorokin and Townsend in the case of the M-5-brane, but here we show
that it holds quite generally, and in particular also in the case of D-branes.Comment: 45 pages, some minor misprints corrected, no modifications otherwis
Weighted stability number of graphs and weighted satisfiability: The two facets of pseudo-Boolean optimization
We exhibit links between pseudo-Boolean optimization, graph theory and logic. We show the equivalence of maximizing a pseudo-Boolean function and finding a maximum weight stable set; symmetrically minimizing a pseudo-Boolean function is shown to be equivalent to solving a weighted satisfiability proble
Impact of super absorbent polymers on early age behavior of ultra-high performance concrete walls
Early age cracking, a common problem for Ultra-High Performance Concrete (UHPC), is caused by Autogenous Shrinkage (AS) and self-desiccation arising from the chemical shrinkage during the cement hydration reactions when the deformation is restrained. However, to avoid the crack development initiated by AS, several solutions can be adopted; one example is the addition of a promising material, considered as an internal curing agent, the Super Absorbent Polymers (SAP) which limits the capillary depressions that can enhance the formation of the crack. In this study the main goal is to mitigate the shrinkage using SAPs in infrastructure under severe conditions. Therefore, a demonstrator wall was built simulating a typical case with high risk of cracking. With the help of fiber optic SOFO sensors embedded in the wall, real-time deformations are recorded and compared the demountable mechanical strain gauges (DEMEC) measurements to further investigate the behavior of SAPs in real scale infrastructure. The amount of extra water (in SAP) needed to mitigate shrinkage was determined by performing chemical shrinkage tests on different cement paste combinations. Tests of autogenous shrinkage were performed on mortars using corrugated tubes and showed that SAPs reduce to some extent the AS. Under restrained conditions via ring tests, SAP specimens did not crack. Therefore, SAPs were found promising towards mitigating the shrinkage and enhancing the early age behavior of concrete for a better durability
Are Occupation Numbers Observable?
The question of whether occupation numbers and momentum distributions of
nucleons in nuclei are observables is considered from an effective field theory
perspective. Field redefinitions lead to variations that imply the answer is
negative, as illustrated in the interacting Fermi gas at low density.
Implications for the interpretation of (e,e'p) experiments with nuclei are
discussed.Comment: 8 pages, revtex4, 4 ps figure
HST/WFPC2 morphologies and color maps of distant luminous infrared galaxies
Using HST/WFPC2 imaging in F606W (or F450W) and F814W filters, we obtained
the color maps in observed frame for 36 distant (0.4<z<1.2) luminous infrared
galaxies (LIRGs), with average star formation rates of ~100 M_sun/yr. Stars and
compact sources are taken as references to align images after correction of
geometric distortion. This leads to an alignment accuracy of 0.15 pixel, which
is a prerequisite for studying the detailed color properties of galaxies with
complex morphologies. A new method is developed to quantify the reliability of
each pixel in the color map without any bias against very red or blue color
regions.Based on analyses of two-dimensional structure and spatially resolved
color distribution, we carried out morphological classification for LIRGs.
About 36% of the LIRGs were classified as disk galaxies and 22% as irregulars.
Only 6 (17%) systems are obvious ongoing major mergers. An upper limit of 58%
was found for the fraction of mergers in LIRGs with all the possible
merging/interacting systems included. Strikingly, the fraction of compact
sources is as high as 25%, similar to that found in optically selected samples.
From their K band luminosities, LIRGs are relatively massive systems, with an
average stellar mass of about 1.1x10^11 solar mass. They are related to the
formation of massive and large disks, from their morphologies and also from the
fact that they represent a significant fraction of distant disks selected by
their sizes. The compact LIRGs show blue cores, which could be associated with
the formation of the central region of these galaxies. We suggest that there
are many massive disks still forming a large fraction of their stellar mass
since z=1. For most of them, their central parts (bulge?) were formed prior to
the formation of their disks.Comment: 20 pages, 14 figures, accepted for publication in A&
Trade Costs and Income in European Regions: Evidence from a regional bilateral trade dataset
Using a New Economic Geography (NEG) model, this study estimates the relationship
between regional per capita income and the market accessibility of regions. This
accessibility cannot be observed directly, so it has to be constructed. We follow a
two-step-procedure as suggested by Redding and Venables (2004) and use results of a
gravity-type model to infer \real market potential". To this end, we make use of a novel
dataset of bi-regional trade
ows between (and within) 254 European NUTS-2 regions
(for 26 European countries excluding Bulgaria and Romania) for the year 2010. In a
second step we test the hypothesis that access to domestic as well as to large foreign
markets increases factor incomes. We find evidence that supports this hypothesis on a
regional level. This also holds when we control for other potential income determinants.
In order for the estimates to be unbiased, we additionally take the spatial structure of
the data into account. Our findings indicate that, although the specification derived
from theory should be able to capture some spatial spillovers, additionally controlling
for spatial autocorrelation in the residuals is necessary to fit the European data. (authors' abstract)Series: Department of Economics Working Paper Serie
The baryonic content and Tully-Fisher relation at z~0.6
[abr.] Using the multi-integral-field spectrograph GIRAFFE at VLT, we
previsouly derived the stellar-mass Tully-Fisher Relation (smTFR) at z~0.6, and
found that the distant relation is systematically offset by roughly a factor of
two toward lower masses. We extend the study of the evolution of the TFR by
establishing the first distant baryonic TFR. To derive gas masses in distant
galaxies, we estimate a gas radius and invert the Schmidt-Kennicutt law between
star formation rate and gas surface densities. We find that gas extends farther
out than the UV light from young stars, a median of ~30%. We present the first
baryonic TFR (bTFR) ever established at intermediate redshift and show that,
within an uncertainty of +/-0.08 dex, the zeropoint of the bTFR does not appear
to evolve between z~0.6 and z=0. The absence of evolution in the bTFR over the
past 6 Gyr implies that no external gas accretion is required for distant
rotating disks to sustain star formation until z=0 and convert most of their
gas into stars. Finally, we confirm that the larger scatter found in the
distant smTFR, and hence in the bTFR, is caused entirely by major mergers. This
scatter results from a transfer of energy from bulk motions in the progenitors,
to random motions in the remnants, generated by shocks during the merging.
Shocks occurring during these events naturally explain the large extent of
ionized gas found out to the UV radius in z~0.6 galaxies. All the results
presented in this paper support the ``spiral rebuilding scenario'' of Hammer
and collaborators, i.e., that a large fraction of local spiral disks have been
reprocessed during major mergers in the past 8 Gyr.Comment: Accepted for publication in A&A, v3 addressing comments from the
refere
GIRAFFE multiple integral field units at VLT: a unique tool to recover velocity fields of distant galaxies
The GIRAFFE spectrograph is unique in providing the integral field
spectroscopy of fifteen distant galaxies at the same time. It has been
successfully implemented at the second VLT unit within the FLAMES facility. We
present GIRAFFE observations acquired during the Guaranteed Time Observation of
the Paris Observatory, using total exposure times ranging from 6 to 12 hours.
The reduced 3D cube of each galaxy has been deconvolved using our new package
DisGal3D. This software has been written using the only assumption that UV
light traces the emission line regions. The comparison between GIRAFFE spectra
and HST imagery allows us to recover details on velocity fields as small as
0.3-0.4 arcsec. It has been successfully tested using Fabry Perot observations
of nearby galaxies purposely redshifted to large distances. We present here
preliminary results for three distant galaxies at 0.45< z < 0.65, whose
velocity fields have been derived with exquisite spectral (R=10000) and spatial
resolutions. Observed velocity fields range from disturbed fields expected in
major merger events to those of regular spiral with minor perturbations. For
the latter, one could accurately derive the dynamical major axis and the
maximal rotational velocity. We conclude that dynamical properties of a large
number of distant galaxies can be routinely derived at VLT. This opens a new
avenue towards the understanding of the galaxy formation and evolution during
the last 8 Gyr.Comment: 4 pages, 3 jpeg figures. to appear in A&
Nonrelativistic scale anomaly, and composite operators with complex scaling dimensions
It is demonstrated that a nonrelativistic quantum scale anomaly manifests
itself in the appearance of composite operators with complex scaling
dimensions. In particular, we study nonrelativistic quantum mechanics with an
inverse square potential and consider a composite s-wave operator O=\psi\psi.
We analytically compute the scaling dimension of this operator and determine
the propagator . The operator O represents an infinite
tower of bound states with a geometric energy spectrum. Operators with higher
angular momenta are briefly discussed.Comment: 18 pages, 3 figures; published versio
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