11,752 research outputs found
A new solid-state logarithmic radiometer
Combination of temperature-compensated logarithmic amplifiers and p-i-n photodiodes operating in zero-bias mode provides lightweight radiometer for detecting spectral intensities encompassing more than three decades over a range of at least 300 to 800 nanometers at low power levels
Measuring software technology
Results are reported from a series of investigations into the effectiveness of various methods and tools used in a software production environment. The basis for the analysis is a project data base, built through extensive data collection and process instrumentation. The project profiles become an organizational memory, serving as a reference point for an active program of measurement and experimentation on software technology
Generalized Hot Enhancons
We review what has been learnt and what remains unknown about the physics of
hot enhancons following studies in supergravity. We recall a rather general
family of static, spherically symmetric, non-extremal enhancon solutions
describing D4 branes wrapped on K3 and discuss physical aspects of the
solutions. We embed these solutions in the six dimensional supergravity
describing Type IIA strings on K3 and generalize them to have arbitrary charge
vector. This allows us to demonstrate the equivalence with a known family of
hot fractional D0 brane solutions, to widen the class of solutions of this
second type and to carry much of the discussion across from the D4 brane
analysis. In particular we argue for the existence of a horizon branch for
these branes.Comment: 25 pages, Late
Evaporation of a Kerr black hole by emission of scalar and higher spin particles
We study the evolution of an evaporating rotating black hole, described by
the Kerr metric, which is emitting either solely massless scalar particles or a
mixture of massless scalar and nonzero spin particles. Allowing the hole to
radiate scalar particles increases the mass loss rate and decreases the angular
momentum loss rate relative to a black hole which is radiating nonzero spin
particles. The presence of scalar radiation can cause the evaporating hole to
asymptotically approach a state which is described by a nonzero value of . This is contrary to the conventional view of black hole
evaporation, wherein all black holes spin down more rapidly than they lose
mass. A hole emitting solely scalar radiation will approach a final asymptotic
state described by . A black hole that is emitting scalar
particles and a canonical set of nonzero spin particles (3 species of
neutrinos, a single photon species, and a single graviton species) will
asymptotically approach a nonzero value of only if there are at least 32
massless scalar fields. We also calculate the lifetime of a primordial black
hole that formed with a value of the rotation parameter , the minimum
initial mass of a primordial black hole that is seen today with a rotation
parameter , and the entropy of a black hole that is emitting scalar or
higher spin particles.Comment: 22 pages, 13 figures, RevTeX format; added clearer descriptions for
variables, added journal referenc
Observation of infinite-range intensity correlations above, at and below the 3D Anderson localization transition
We investigate long-range intensity correlations on both sides of the
Anderson transition of classical waves in a three-dimensional (3D) disordered
material. Our ultrasonic experiments are designed to unambiguously detect a
recently predicted infinite-range C0 contribution, due to local density of
states fluctuations near the source. We find that these C0 correlations, in
addition to C2 and C3 contributions, are significantly enhanced near mobility
edges. Separate measurements of the inverse participation ratio reveal a link
between C0 and the anomalous dimension \Delta_2, implying that C0 may also be
used to explore the critical regime of the Anderson transition.Comment: 13 pages, 11 figures (main text plus supplemental information).
Updated version includes an improved introductory paragraph, minor text
revisions, a revised title and additional supplemental information on the
experimental detail
Rotating Black Holes in Higher Dimensions with a Cosmological Constant
We present the metric for a rotating black hole with a cosmological constant
and with arbitrary angular momenta in all higher dimensions. The metric is
given in both Kerr-Schild and Boyer-Lindquist form. In the Euclidean-signature
case, we also obtain smooth compact Einstein spaces on associated S^{D-2}
bundles over S^2, infinitely many for each odd D\ge 5. Applications to string
theory and M-theory are indicated.Comment: 8 pages, Latex. Short version, with more compact notation, of
hep-th/0404008. To appear in Phys. Rev. Let
Numerical modeling of dynamic powder compaction using the Kawakita equation of state
Dynamic powder compaction is analyzed using the assumption that the powder behaves, while it is being compacted, like a hydrodynamic fluid in which deviatoric stress and heat conduction effects can be ignored throughout the process. This enables techniques of computational fluid dynamics such the equilibrium flux method to be used as a modeling tool. The equation of state of the powder under compression is assumed to be a modified version of the Kawakita loading curve. Computer simulations using this model are performed for conditions matching as closely as possible with those from experiments by Page and Killen [Powder Metall. 30, 233 (1987)]. The numerical and experimental results are compared and a surprising degree of qualitative agreement is observed
Black Hole Motion in Entropic Reformulation of General Relativity
We consider a system of black holes -- a simplest substitute of a system of
point particles in the mechanics of general relativity -- and try to describe
their motion with the help of entropic action: a sum of the areas of black hole
horizons. We demonstrate that such description is indeed consistent with the
Newton's laws of motion and gravity, modulo numerical coefficients, which
coincide but seem different from unity. Since a large part of the modern
discussion of entropic reformulation of general relativity is actually based on
dimensional considerations, for making a next step it is crucially important to
modify the argument, so that these dimensionless parameters acquire correct
values.Comment: 6 page
Locating Overlap Information in Quantum Systems
When discussing the black hole information problem the term ``information
flow'' is frequently used in a rather loose fashion. In this article I attempt
to make this notion more concrete. I consider a Hilbert space which is
constructed as a tensor product of two subspaces (representing for example
inside and outside the black hole). I discuss how the system has the capacity
to contain information which is in NEITHER of the subspaces. I attempt to
quantify the amount of information located in each of the two subspaces, and
elsewhere, and analyze the extent to which unitary evolution can correspond to
``information flow''. I define the notion of ``overlap information'' which
appears to be well suited to the problem.Comment: 25 pages plain LaTeX, no figures. Imperial/TP/93-94/2
Information-theoretic determination of ponderomotive forces
From the equilibrium condition applied to an isolated
thermodynamic system of electrically charged particles and the fundamental
equation of thermodynamics () subject
to a new procedure, it is obtained the Lorentz's force together with
non-inertial terms of mechanical nature. Other well known ponderomotive forces,
like the Stern-Gerlach's force and a force term related to the Einstein-de
Haas's effect are also obtained. In addition, a new force term appears,
possibly related to a change in weight when a system of charged particles is
accelerated.Comment: 10 page
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