15,667 research outputs found
Role of Galaxy Mergers in Cosmic Star Formation History
We present a morphology study of intermediate-redshift (0.2<z<1.2) luminous
infrared galaxies (LIRGs) and general field galaxies in the GOODS fields using
a revised asymmetry measurement method optimized for deep fields. By taking
careful account of the importance of the underlying sky-background structures,
our new method does not suffer from systematic bias and offers small
uncertainties. By redshifting local LIRGs and low-redshift GOODS galaxies to
different higher redshifts, we have found that the redshift dependence of the
galaxy asymmetry due to surface-brightness dimming is a function of the
asymmetry itself, with larger corrections for more asymmetric objects. By
applying redshift-, IR-luminosity- and optical-brightness-dependent asymmetry
corrections, we have found that intermediate-redshift LIRGs generally show
highly asymmetric morphologies, with implied merger fractions ~50% up to z=1.2,
although they are slightly more symmetric than local LIRGs. For general field
galaxies, we find an almost constant relatively high merger fraction (20-30%).
The B-band LFs of galaxy mergers are derived at different redshifts up to z=1.2
and confirm the weak evolution of the merger fraction after breaking the
luminosity-density degeneracy. The IR luminosity functions (LFs) of galaxy
mergers are also derived, indicating a larger merger fraction at higher IR
luminosity. The integral of the merger IR LFs indicates a dramatic evolution of
the merger-induced IR energy density [(1+z)^(5-6)}], and that galaxy mergers
start to dominate the cosmic IR energy density at z>~1.Comment: Accepted for publication in ApJ, 25 pages, 23 figures (2 colors). The
high-resolution pdf is at
http://cztsy.as.arizona.edu/~yong/Research/SHI_MERGER.pd
Gluino zero-modes for non-trivial holonomy calorons
We couple fermion fields in the adjoint representation (gluinos) to the SU(2)
gauge field of unit charge calorons defined on R^3 x S_1. We compute
corresponding zero-modes of the Dirac equation. These are relevant in
semiclassical studies of N=1 Super-symmetric Yang-Mills theory. Our formulas,
show that, up to a term proportional to the vector potential, the modes can be
constructed by different linear combinations of two contributions adding up to
the total caloron field strength.Comment: 17 pages, 3 Postscript figures, late
Optical photometry of the UCM Lists I and II
We present Johnson B CCD photometry for the whole sample of galaxies of the
Universidad Complutense de Madrid (UCM) Survey Lists I and II. They constitute
a well-defined and complete sample of galaxies in the Local Universe with
active star formation. The data refer to 191 S0 to Irr galaxies at an averaged
redshift of 0.027, and complement the already published Gunn r, J and K
photometries. In this paper the observational and reduction features are
discussed in detail, and the new colour information is combined to search for
clues on the properties of the galaxies, mainly by comparing our sample with
other surveys.Comment: 14 pages, 7 PostScript figures, accepted for publication in A&AS,
also available vi ftp at ftp://cutrex.fis.ucm.es/pub/OUT/pag/PAPERS
Towards a Quantum Software Modeling Language
We set down the principles behind a modeling language for quantum software. We present a minimal set of extensions to the well-known Unified Modeling Language (UML) that allows it to effectively model quantum software. These extensions are separate and independent of UML as a whole. As such they can be used to extend any other software modeling language, or as a basis for a completely new language. We argue that these extensions are both necessary and sufficient to model, abstractly, any piece of quantum software. Finally, we provide a small set of examples that showcase the effectiveness of the extension set
Comparison of |Q|=1 and |Q|=2 gauge-field configurations on the lattice four-torus
It is known that exactly self-dual gauge-field configurations with
topological charge |Q|=1 cannot exist on the untwisted continuum 4-torus. We
explore the manifestation of this remarkable fact on the lattice 4-torus for
SU(3) using advanced techniques for controlling lattice discretization errors,
extending earlier work of De Forcrand et. al. for SU(2). We identify three
distinct signals for the instability of |Q|=1 configurations, and show that
these manifest themselves early in the cooling process, long before the
would-be instanton has shrunk to a size comparable to the lattice
discretization threshold. These signals do not appear for our |Q|=2
configurations. This indicates that these signals reflect the truly global
nature of the instability, rather than local discretization effects.
Monte-Carlo generated SU(3) gauge field configurations are cooled to the
self-dual limit using an O(a^4)-improved gauge action chosen to have small but
positive O(a^6) errors. This choice prevents lattice discretization errors from
destroying instantons provided their size exceeds the dislocation threshold of
the cooling algorithm. Lattice discretization errors are evaluated by comparing
the O(a^4)-improved gauge-field action with an O(a^4)-improved action
constructed from the square of an O(a^4)-improved lattice field-strength
tensor, thus having different O(a^6) discretization errors. The number of
action-density peaks, the instanton size and the topological charge of
configurations is monitored. We observe a fluctuation in the total topological
charge of |Q|=1 configurations, and demonstrate that the onset of this unusual
behavior corresponds with the disappearance of multiple-peaks in the action
density. At the same time discretization errors are minimal.Comment: 12 pages, 9 figures, submitted to Phys. Rev.
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