23,489 research outputs found
Retrieval information file relating to assigned frequencies, part 2 Final report, Jan. - Sep. 1969
Retrieval information file relating to assigned frequencies for use on IBM 360 compute
Mesoscopic Mechanical Resonators as Quantum Non-Inertial Reference Frames
An atom attached to a micrometer-scale wire that is vibrating at a frequency
of 100 MHz and with displacement amplitude 1 nm experiences an acceleration
magnitude 10^9 ms^-2, approaching the surface gravity of a neutron star. As one
application of such extreme non-inertial forces in a mesoscopic setting, we
consider a model two-path atom interferometer with one path consisting of the
100 MHz vibrating wire atom guide. The vibrating wire guide serves as a
non-inertial reference frame and induces an in principle measurable phase shift
in the wave function of an atom traversing the wire frame. We furthermore
consider the effect on the two-path atom wave interference when the vibrating
wire is modeled as a quantum object, hence functioning as a quantum
non-inertial reference frame. We outline a possible realization of the
vibrating wire, atom interferometer using a superfluid helium quantum
interference setup.Comment: Published versio
On the mass of a Kerr-anti-de Sitter spacetime in D dimensions
We show how to compute the mass of a Kerr-anti-de Sitter spacetime with
respect to the anti-de Sitter background in any dimension, using a
superpotential which has been derived from standard Noether identities. The
calculation takes no account of the source of the curvature and confirms
results obtained for black holes via the first law of thermodynamics.Comment: minor changes; accepted by CQ
Superpotentials from variational derivatives rather than Lagrangians in relativistic theories of gravity
The prescription of Silva to derive superpotential equations from variational
derivatives rather than from Lagrangian densities is applied to theories of
gravity derived from Lovelock Lagrangians in the Palatini representation.
Spacetimes are without torsion and isolated sources of gravity are minimally
coupled. On a closed boundary of spacetime, the metric is given and the
connection coefficients are those of Christoffel. We derive equations for the
superpotentials in these conditions. The equations are easily integrated and we
give the general expression for all superpotentials associated with Lovelock
Lagrangians. We find, in particular, that in Einstein's theory, in any number
of dimensions, the superpotential, valid at spatial and at null infinity, is
that of Katz, Bicak and Lynden-Bell, the KBL superpotential. We also give
explicitly the superpotential for Gauss-Bonnet theories of gravity. Finally, we
find a simple expression for the superpotential of Einstein-Gauss-Bonnet
theories with an anti-de Sitter background: it is minus the KBL superpotential,
confirming, as it should, the calculation of the total mass-energy of spacetime
at spatial infinity by Deser and Tekin.Comment: Scheduled to appear in Class. Quantum Grav. August 200
On the Evolutionary History of Stars and their Fossil Mass and Light
The total extragalactic background radiation can be an important test of the
global star formation history (SFH). Using direct observational estimates of
the SFH, along with standard assumptions about the initial mass function (IMF),
we calculate the total extragalactic background radiation and the observed
stellar density today. We show that plausible SFHs allow a significant range in
each quantity, but that their ratio is very tightly constrained. Current
estimates of the stellar mass and extragalactic background are difficult to
reconcile, as long as the IMF is fixed to the Salpeter slope above 1 Msun. The
joint confidence interval of these two quantities only agrees with that
determined from the allowed range of SFH fits at the 3-sigma level, and for our
best-fit values the discrepancy is about a factor of two. Alternative energy
sources that contribute to the background, such as active galactic nuclei
(AGN), Population III stars, or decaying particles, appear unlikely to resolve
the discrepancy. However, changes to the IMF allow plausible solutions to the
background problem. The simplest is an average IMF with an increased
contribution from stars around 1.5--4 Msun. A ``paunchy'' IMF of this sort
could emerge as a global average if low mass star formation is suppressed in
galaxies experiencing rapid starbursts. Such an IMF is consistent with
observations of star-forming regions, and would help to reconcile the fossil
record of star formation with the directly observed SFH.Comment: 21 pages, 7 figures, 3 tables; submitted to Monthly Notice
Mass and angular momenta of Kerr anti-de Sitter spacetimes in Einstein-Gauss-Bonnet theory
We compute the mass and angular momenta of rotating anti-de Sitter spacetimes
in Einstein-Gauss-Bonnet theory of gravity using a superpotential derived from
standard Noether identities. The calculation relies on the fact that the
Einstein and Einstein-Gauss-Bonnet vacuum equations are the same when
linearized on maximally symmetric backgrounds and uses the recently discovered
D-dimensional Kerr-anti-de Sitter solutions to Einstein's equations
Some Aspects of New CDM Models and CDM Detection Methods
We briefly review some recent Cold Dark Matter (CDM) models. Our main focus
are charge symmetric models of WIMPs which are not the standard SUSY LSP's
(Lightest Supersymmetric Partners). We indicate which experiments are most
sensitive to certain aspects of the models. In particular we discuss the
manifestations of the new models in neutrino telescopes and other set-ups. We
also discuss some direct detection experiments and comment on measuring the
direction of recoil ions--which is correlated with the direction of the
incoming WIMP. This could yield daily variations providing along with the
annual modulation signatures for CDM.Comment: 14 page
Parametrically excited "Scars" in Bose-Einstein condensates
Parametric excitation of a Bose-Einstein condensate (BEC) can be realized by
periodically changing the interaction strength between the atoms. Above some
threshold strength, this excitation modulates the condensate density. We show
that when the condensate is trapped in a potential well of irregular shape,
density waves can be strongly concentrated ("scarred") along the shortest
periodic orbits of a classical particle moving within the confining potential.
While single-particle wave functions of systems whose classical counterpart is
chaotic may exhibit rich scarring patterns, in BEC, we show that nonlinear
effects select mainly those scars that are locally described by stripes.
Typically, these are the scars associated with self retracing periodic orbits
that do not cross themselves in real space. Dephasing enhances this behavior by
reducing the nonlocal effect of interference
Hadron Masses and Screening from AdS Wilson Loops
We show that in strongly coupled N=4 SYM the binding energy of a heavy and a
light quark is independent of the strength of the coupling constant. As a
consequence we are able to show that in the presence of light quarks the analog
of the QCD string can snap and color charges are screened. The resulting
neutral mesons interact with each other only via pion exchange and we estimate
the massesComment: 4 pages, revte
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