8,620 research outputs found
The luminosity function of the brightest galaxies in the IRAS survey
Results from a study of the far infrared properties of the brightest galaxies in the IRAS survey are described. There is a correlation between the infrared luminosity and the infrared to optical luminosity ratio and between the infrared luminosity and the far infrared color temperature in these galaxies. The infrared bright galaxies represent a significant component of extragalactic objects in the local universe, being comparable in space density to the Seyferts, optically identified starburst galaxies, and more numerous than quasars at the same bolometric luminosity. The far infrared luminosity in the local universe is approximately 25% of the starlight output in the same volume
Characteristics of UGC galaxies detected by IRAS
Infrared Astronomy Satellite (IRAS) detection rates at 60 microns were determined for the Uppsala General Catalog of Galaxies (Nilson 1973; the UCG). Late-type spirals, characterized by a normal IR/B ratio of approximately 0.6, are detected to a velocity of approximately 6000 km/s for L sub B = L sub *. Contrary to the situation for IRAS-selected galaxy samples, little evidence was found for a correlation between IR/B and 60/100 microns in this large optically-selected sample. Thus a significant fraction of the IRAS-measured far-infrared flux from normal spirals must originate in the diffuse interstellar medium, heated by the interstellar radiation field. Support was not found for Burstein and Lebofsky's (1986) conclusion that spiral disks are optically thick in the far-infrared
Resonance Interaction Induced by Metal Surfaces Catalyses Atom Pair Breakage
We present the theory for retarded resonance interaction between two
identical atoms at arbitrary positions near a metal surface. The dipole-dipole
resonance interaction force that binds isotropically excited atom pairs
together in free space may turn repulsive close to an ideal (totally
reflecting) metal surface. On the other hand, close to an infinitely permeable
surface it may turn more attractive. We illustrate numerically how the
dipole-dipole resonance interaction between two oxygen atoms near a metal
surface may provide a repulsive energy of the same order of magnitude as the
ground-state binding energy of an oxygen molecule. As a complement we also
present results from density-functional theory.Comment: 5 pages, 5 figure
Rigid Calabi-Yau threefolds, Picard Eisenstein series and instantons
Type IIA string theory compactified on a rigid Calabi-Yau threefold gives
rise to a classical moduli space that carries an isometric action of U(2,1).
Various quantum corrections break this continuous isometry to a discrete
subgroup. Focussing on the case where the intermediate Jacobian of the
Calabi-Yau admits complex multiplication by the ring of quadratic imaginary
integers O_d, we argue that the remaining quantum duality group is an
arithmetic Picard modular group PU(2,1;O_d). Based on this proposal we
construct an Eisenstein series invariant under this duality group and study its
non-Abelian Fourier expansion. This allows the prediction of non-perturbative
effects, notably the contribution of D2- and NS5-brane instantons. The present
work extends our previous analysis in 0909.4299 which was restricted to the
special case of the Gaussian integers O_1=Z[i].Comment: 8 pages, for the proceedings of Quantum Theories and Symmetries V
Self-Policing: Dissemination and Adoption of Police Eyewitness Policies in Virginia
Professional policing organizations emphasize the importance of the adoption of sound police policies and procedures, but traditionally doing so has been left to individual agencies. State and local government typically does not closely regulate police, and neither federal constitutional rulings nor state law typically sets out in any detail the practices that police should follow. Thus, law enforcement agencies must themselves draft and disseminate policy. This paper presents the results of studies used to assess the adoption of eyewitness identification policies by law enforcement agencies in Virginia. Policymakers were focused on this problem because Virginia experienced a series of DNA exonerations in cases involving eyewitness misidentifications. In 2005, lawmakers enacted a law that required agencies to have some written policy in place. However, there was little guidance on what that policy should be. To remedy this problem, the state law enforcement policy agency, the Virginia Department of Criminal Justice Services (DCJS) promulgated, in 2011, a detailed model policy on eyewitness procedure. Nevertheless, as reported in a 2013 study, those model practices were only haltingly adopted. In particular, many agencies did not use blind or blinded lineups, in which the administrator does not know which photo is that of a suspect or cannot view which photo the eyewitness is examining. In Fall 2018, all of the over-three hundred law enforcement agencies in Virginia had their policies on this subject requested, using the state freedom of information law. The results show that there has now been widespread adoption of the DCJS model policy. Improved eyewitness identification practices have been adopted by the vast majority of agencies, including large and small agencies. This Article concludes by asking what contributed to the extensive dissemination of a model police policy, and what its implications are for improving police policy and practice without the use of regulation
Dynamics of quantum systems
A relation between the eigenvalues of an effective Hamilton operator and the
poles of the matrix is derived which holds for isolated as well as for
overlapping resonance states. The system may be a many-particle quantum system
with two-body forces between the constituents or it may be a quantum billiard
without any two-body forces. Avoided crossings of discrete states as well as of
resonance states are traced back to the existence of branch points in the
complex plane. Under certain conditions, these branch points appear as double
poles of the matrix. They influence the dynamics of open as well as of
closed quantum systems. The dynamics of the two-level system is studied in
detail analytically as well as numerically.Comment: 21 pages 7 figure
Global properties of the nearby spiral M101
M101 (NGC 5457) is a classic Sc I spiral galaxy located suffiently nearby, 6.8 Mpc, that its structure can be studied even with the coarse angular resolution of the Infrared Astronomy Satellite (IRAS). The global infrared properties of M101 are addressed including the radial dependence of its infrared emission
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