3,007 research outputs found
Spin induced multipole moments for the gravitational wave flux from binary inspirals to third Post-Newtonian order
Using effective field theory techniques we calculate the source multipole
moments needed to obtain the spin contributions to the power radiated in
gravitational waves from inspiralling compact binaries to third Post-Newtonian
order (3PN). The multipoles depend linearly and quadratically on the spins and
include both spin(1)spin(2) and spin(1)spin(1) components. The results in this
paper provide the last missing ingredient required to determine the phase
evolution to 3PN including all spin effects which we will report in a separate
paper.Comment: 35 pages, 7 figures. Published versio
Universal Behaviour of the Superfluid Fraction and Tc of He-3 in 99.5% Open Aerogel
We have investigated the superfluid transition of He-3 in a 99.5% porosity
silica aerogel. This very dilute sample shows behaviour intermediary between
bulk He-3 and He-3 confined to the denser aerogels previously studied. We
present data on both the superfluid transition temperature and the superfluid
density and compare our results with previous measurements. Finally, we show
that the suppression of the superfluid transition temperature and suppression
of the superfluid density of He-3 in aerogel follow a universal relation for a
range of aerogel samples.Comment: 4 pages, 5 figures; 1 new figure, minor change
Differential Light Shift Cancellation in a Magnetic-Field-Insensitive Transition of Rb
We demonstrate near-complete cancellation of the differential light shift of
a two-photon magnetic-field-insensitive microwave hyperfine (clock) transition
in Rb atoms trapped in an optical lattice. Up to of the
differential light shift is canceled while maintaining magnetic-field
insensitivity. This technique should have applications in quantum information
and frequency metrology.Comment: 5 pages, 4 figure
Conditional probabilities with Dirac observables and the problem of time in quantum gravity
We combine the "evolving constants" approach to the construction of
observables in canonical quantum gravity with the Page--Wootters formulation of
quantum mechanics with a relational time for generally covariant systems. This
overcomes the objections levied by Kucha\v{r} against the latter formalism. The
construction is formulated entirely in terms of Dirac observables, avoiding in
all cases the physical observation of quantities that do not belong in the
physical Hilbert space. We work out explicitly the example of the parameterized
particle, including the calculation of the propagator. The resulting theory
also predicts a fundamental mechanism of decoherence.Comment: 4 pages, no figures, RevTe
Next to leading order spin-orbit effects in the motion of inspiralling compact binaries
Using effective field theory (EFT) techniques we calculate the
next-to-leading order (NLO) spin-orbit contributions to the gravitational
potential of inspiralling compact binaries. We use the covariant spin
supplementarity condition (SSC), and explicitly prove the equivalence with
previous results by Faye et al. in arXiv:gr-qc/0605139. We also show that the
direct application of the Newton-Wigner SSC at the level of the action leads to
the correct dynamics using a canonical (Dirac) algebra. This paper then
completes the calculation of the necessary spin dynamics within the EFT
formalism that will be used in a separate paper to compute the spin
contributions to the energy flux and phase evolution to NLO.Comment: 25 pages, 4 figures, revtex4. v2: minor changes, refs. added. To
appear in Class. Quant. Gra
Optimization of photon storage fidelity in ordered atomic arrays
A major application for atomic ensembles consists of a quantum memory for
light, in which an optical state can be reversibly converted to a collective
atomic excitation on demand. There exists a well-known fundamental bound on the
storage error, when the ensemble is describable by a continuous medium governed
by the Maxwell-Bloch equations. The validity of this model can break down,
however, in systems such as dense, ordered atomic arrays, where strong
interference in emission can give rise to phenomena such as subradiance and
"selective" radiance. Here, we develop a general formalism that finds the
maximum storage efficiency for a collection of atoms with discrete, known
positions, and a given spatial mode in which an optical field is sent. As an
example, we apply this technique to study a finite two-dimensional square array
of atoms. We show that such a system enables a storage error that scales with
atom number like ,
and that, remarkably, an array of just atoms in principle allows
for an efficiency comparable to a disordered ensemble with optical depth of
around 600.Comment: paper is now identical to published versio
Non-Relativistic Gravitation: From Newton to Einstein and Back
We present an improvement to the Classical Effective Theory approach to the
non-relativistic or Post-Newtonian approximation of General Relativity. The
"potential metric field" is decomposed through a temporal Kaluza-Klein ansatz
into three NRG-fields: a scalar identified with the Newtonian potential, a
3-vector corresponding to the gravito-magnetic vector potential and a 3-tensor.
The derivation of the Einstein-Infeld-Hoffmann Lagrangian simplifies such that
each term corresponds to a single Feynman diagram providing a clear physical
interpretation. Spin interactions are dominated by the exchange of the
gravito-magnetic field. Leading correction diagrams corresponding to the 3PN
correction to the spin-spin interaction and the 2.5PN correction to the
spin-orbit interaction are presented.Comment: 10 pages, 3 figures. v2: published version. v3: Added a computation
of Einstein-Infeld-Hoffmann in higher dimensions within our improved ClEFT
which partially confirms and partially corrects a previous computation. See
notes added at end of introductio
Fundamental decoherence from relational time in discrete quantum gravity: Galilean covariance
We have recently argued that if one introduces a relational time in quantum
mechanics and quantum gravity, the resulting quantum theory is such that pure
states evolve into mixed states. The rate at which states decohere depends on
the energy of the states. There is therefore the question of how this can be
reconciled with Galilean invariance. More generally, since the relational
description is based on objects that are not Dirac observables, the issue of
covariance is of importance in the formalism as a whole. In this note we work
out an explicit example of a totally constrained, generally covariant system of
non-relativistic particles that shows that the formula for the relational
conditional probability is a Galilean scalar and therefore the decoherence rate
is invariant.Comment: 10 pages, RevTe
A Bose-Einstein Condensate in a Uniform Light-induced Vector Potential
We use a two-photon dressing field to create an effective vector gauge
potential for Bose-condensed Rb atoms in the F=1 hyperfine ground state. The
dressed states in this Raman field are spin and momentum superpositions, and we
adiabatically load the atoms into the lowest energy dressed state. The
effective Hamiltonian of these neutral atoms is like that of charged particles
in a uniform magnetic vector potential, whose magnitude is set by the strength
and detuning of Raman coupling. The spin and momentum decomposition of the
dressed states reveals the strength of the effective vector potential, and our
measurements agree quantitatively with a simple single-particle model. While
the uniform effective vector potential described here corresponds to zero
magnetic field, our technique can be extended to non-uniform vector potentials,
giving non-zero effective magnetic fields.Comment: 5 pages, submitted to Physical Review Letter
Robust superfluid phases of 3He in aerogel
Within a phenomenological approach possible forms of the order parameter of
the superfluid phases of 3He in a vicinity of the transition temperature are
discussed. Effect of aerogel is described by a random tensor field interacting
with the orbital part of the order parameter. With respect to their interaction
with the random tensor field a group of "robust" order parameters which can
maintain long-range order in a presence of the random field is specified.
Robust order parameters, corresponding to Equal Spin Pairing (ESP) states are
found and proposed as candidates for the observed A-like superfluid phase of
liquid 3He in aerogel.Comment: 5 pages, prepared for QFS 200
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