11,054 research outputs found
Worldsheet Matter Superfields on Half-Shell
In this paper we discuss some of the effects of using "unidexterous"
worldsheet superfields, which satisfy worldsheet differential constraints and
so are partly on-shell, i.e., on half-shell. Most notably, this results in a
stratification of the field space that reminds of "brane-world" geometries.
Linear dependence on such superfields provides a worldsheet generalization of
the super-Zeeman effect. In turn, non-linear dependence yields additional
left-right asymmetric dynamical constraints on the propagating fields, again in
a stratified fashion.Comment: 15 pages, 2 figures; minor algebraic correction
Periodic variations in the colours of the classical T Tauri star RW Aur A
The classical T Tauri star RW Aur A is an irregular variable with a large
amplitude in all photometric bands. In an extended series of photometric data
we found small-amplitude periodic variations in the blue colours of the star,
with a period of 2.64 days. The period was relatively stable over several
years. The amplitude of the periodic signal is 0.21 mag in U-V, 0.07 mag in
B-V, and about 0.02 mag in V-R and V-I. No periodicity was found in the V
magnitude. The relevance of this photometric period to the recently discovered
periodicity in spectral features of the star is discussed, and the hypothesis
of a hot spot is critically considered.Comment: 5 pages, 8 figures, uses new aa.cls, accepted for publication in
Astronomy and Astrophysic
Lifetime Differences in Heavy Mesons With Time Independent Measurements
Heavy meson pairs produced in the decays of heavy quarkonium resonances at e+
e- machines (beauty and tau-charm factories) have the useful property that the
two mesons are in the CP-correlated states. By tagging one of the mesons as a
CP eigenstate, a lifetime difference of heavy neutral meson mass eigenstates
width difference may be determined by measuring the leptonic branching ratio of
the other meson. We discuss the use of this and related methods both in the
case where time dependent mixing is small and when it is significant. We
consider the impact of possible CP-violating effects and present the complete
results for CP-entangled decay rates with CP-violation taken into account.Comment: 14 pages, 0 figures; 2 references added, results unchange
Cold Collision Frequency Shift in Two-Dimensional Atomic Hydrogen
We report a measurement of the cold collision frequency shift in atomic
hydrogen gas adsorbed on the surface of superfluid 4He at T<=90 mK. Using
two-photon electron and nuclear magnetic resonance in 4.6 T field we separate
the resonance line shifts due to the dipolar and exchange interactions, both
proportional to surface density sigma. We find the clock shift Delta v_c =
-1.0(1)x10^-7 Hz cm^-2 x sigma, which is about 100 times smaller than the value
predicted by the mean field theory and known scattering lengths in the 3D case.Comment: 4 pages, 3 figure
The Schwarzschild black hole as a point particle
The description of a point mass in general relativity (GR) is given in the
framework of the field formulation of GR where all the dynamical fields,
including the gravitational field, are considered in a fixed background
spacetime. With the use of stationary (not static) coordinates non-singular at
the horizon, the Schwarzschild solution is presented as a point-like field
configuration in a whole background Minkowski space. The requirement of a
stable -causality stated recently in [J.B.Pitts and W.C.Schieve, Found.
Phys., v. 34, 211 (2004)] is used essentially as a criterion for testing
configurations.Comment: LATEX, 8 pages, no figure
A note on the Deser-Tekin charges
Perturbed equations for an arbitrary metric theory of gravity in
dimensions are constructed in the vacuum of this theory. The nonlinear part
together with matter fields are a source for the linear part and are treated as
a total energy-momentum tensor. A generalized family of conserved currents
expressed through divergences of anti-symmetrical tensor densities
(superpotentials) linear in perturbations is constructed. The new family
generalizes the Deser and Tekin currents and superpotentials in quadratic
curvature gravity theories generating Killing charges in dS and AdS vacua. As
an example, the mass of the -dimensional Schwarzschild black hole in an
effective AdS spacetime (a solution in the Einstein-Gauss-Bonnet theory) is
examined.Comment: LATEX, 7 pages, no figure
Observation of Phase Fluctuations in Bose-Einstein Condensates
The occurrence of phase fluctuations due to thermal excitations in
Bose-Einstein condensates (BECs) is studied for a variety of temperatures and
trap geometries. We observe the statistical nature of the appearence of phase
fluctuations and characterize the dependence of their average value on
temperature, number of particles and the trapping potential. We find pronounced
phase fluctuations for condensates in very elongated traps in a broad
temperature range. The results are of great importance for the realization of
BEC in quasi 1D geometries, for matter wave interferometry with BECs, as well
as for coherence properties of guided atom laser beams.Comment: 4 pages, 4 figure
Non-Destructive Probing of Rabi Oscillations on the Cesium Clock Transition near the Standard Quantum Limit
We report on non-destructive observation of Rabi oscillations on the Cs clock
transition. The internal atomic state evolution of a dipole-trapped ensemble of
cold atoms is inferred from the phase shift of a probe laser beam as measured
using a Mach-Zehnder interferometer. We describe a single color as well as a
two-color probing scheme. Using the latter, measurements of the collective
pseudo-spin projection of atoms in a superposition of the clock states are
performed and the observed spin fluctuations are shown to be close to the
standard quantum limit.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
Letter
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