3,439 research outputs found
Towers of Gravitational Theories
In this essay we introduce a theoretical framework designed to describe black
hole dynamics. The difficulties in understanding such dynamics stems from the
proliferation of scales involved when one attempts to simultaneously describe
all of the relevant dynamical degrees of freedom. These range from the modes
that describe the black hole horizon, which are responsible for dissipative
effects, to the long wavelength gravitational radiation that drains mechanical
energy from macroscopic black hole bound states. We approach the problem from a
Wilsonian point of view, by building a tower of theories of gravity each of
which is valid at different scales. The methodology leads to multiple new
results in diverse topics including phase transitions of Kaluza-Klein black
holes and the interactions of spinning black hole in non-relativistic orbits.
Moreover, our methods tie together speculative ideas regarding dualities for
black hole horizons to real physical measurements in gravitational wave
detectors.Comment: Awarded second prize for 2006 Gravity Research Foundation essay
contes
Effective field theory approach to Casimir interactions on soft matter surfaces
We utilize an effective field theory approach to calculate Casimir
interactions between objects bound to thermally fluctuating fluid surfaces or
interfaces. This approach circumvents the complicated constraints imposed by
such objects on the functional integration measure by reverting to a point
particle representation. To capture the finite size effects, we perturb the
Hamiltonian by DH that encapsulates the particles' response to external fields.
DH is systematically expanded in a series of terms, each of which scales
homogeneously in the two power counting parameters: \lambda \equiv R/r, the
ratio of the typical object size (R) to the typical distance between them (r),
and delta=kB T/k, where k is the modulus characterizing the surface energy. The
coefficients of the terms in DH correspond to generalized polarizabilities and
thus the formalism applies to rigid as well as deformable objects.
Singularities induced by the point particle description can be dealt with using
standard renormalization techniques. We first illustrate and verify our
approach by re-deriving known pair forces between circular objects bound to
films or membranes. To demonstrate its efficiency and versatility, we then
derive a number of new results: The triplet interactions present in these
systems, a higher order correction to the film interaction, and general scaling
laws for the leading order interaction valid for objects of arbitrary shape and
internal flexibility.Comment: 4 pages, 1 figur
Relative Entropy: Free Energy Associated with Equilibrium Fluctuations and Nonequilibrium Deviations
Using a one-dimensional macromolecule in aqueous solution as an illustration,
we demonstrate that the relative entropy from information theory, , has a natural role in the energetics of equilibrium and
nonequilibrium conformational fluctuations of the single molecule. It is
identified as the free energy difference associated with a fluctuating density
in equilibrium, and is associated with the distribution deviate from the
equilibrium in nonequilibrium relaxation. This result can be generalized to any
other isothermal macromolecular systems using the mathematical theories of
large deviations and Markov processes, and at the same time provides the
well-known mathematical results with an interesting physical interpretations.Comment: 5 page
HST/NICMOS Observations of Fast Infrared Flickering in the Microquasar GRS 1915+105
We report infrared observations of the microquasar GRS 1915+105 using the
NICMOS instrument of the Hubble Space Telescope during 9 visits in April-June
2003. During epochs of high X-ray/radio activity near the beginning and end of
this period, we find that the \um infrared flux is generally low ( mJy) and relatively steady. However, during the X-ray/radio ``plateau''
state between these epochs, we find that the infrared flux is significantly
higher ( mJy), and strongly variable. In particular, we find events
with amplitudes % occurring on timescales of s
(e-folding timescales of s). These flickering timescales are several
times faster than any previously-observed infrared variability in GRS 1915+105
and the IR variations exceed corresponding X-ray variations at the same () timescale. These results suggest an entirely new type of infrared
variability from this object. Based on the properties of this flickering, we
conclude that it arises in the plateau-state jet outflow itself, at a distance
AU from the accretion disk. We discuss the implications of this work and
the potential of further flickering observations for understanding jet
formation around black holes.Comment: 19 pages, incl. 4 figures; accepted for publication in Ap
A nonlinear scalar model of extreme mass ratio inspirals in effective field theory I. Self force through third order
The motion of a small compact object in a background spacetime is
investigated in the context of a model nonlinear scalar field theory. This
model is constructed to have a perturbative structure analogous to the General
Relativistic description of extreme mass ratio inspirals (EMRIs). We apply the
effective field theory approach to this model and calculate the finite part of
the self force on the small compact object through third order in the ratio of
the size of the compact object to the curvature scale of the background (e.g.,
black hole) spacetime. We use well-known renormalization methods and
demonstrate the consistency of the formalism in rendering the self force finite
at higher orders within a point particle prescription for the small compact
object. This nonlinear scalar model should be useful for studying various
aspects of higher-order self force effects in EMRIs but within a comparatively
simpler context than the full gravitational case. These aspects include
developing practical schemes for higher order self force numerical
computations, quantifying the effects of transient resonances on EMRI waveforms
and accurately modeling the small compact object's motion for precise
determinations of the parameters of detected EMRI sources.Comment: 30 pages, 8 figure
Finite size corrections to the radiation reaction force in classical electrodynamics
We introduce an effective field theory approach that describes the motion of
finite size objects under the influence of electromagnetic fields. We prove
that leading order effects due to the finite radius of a spherically
symmetric charge is order rather than order in any physical model, as
widely claimed in the literature. This scaling arises as a consequence of
Poincar\'e and gauge symmetries, which can be shown to exclude linear
corrections. We use the formalism to calculate the leading order finite size
correction to the Abraham-Lorentz-Dirac force.Comment: 4 pages, 2 figure
Lepton Flavor Violation and the Tau Neutrino Mass
We point out that, in the left-right symmetric model of weak interaction, if
mass is in the keV to MeV range, there is a strong correlation
between rare decays such as and
the mass. In particular, we point out that a large range of
masses are forbidden by the cosmological constraints on
in combination with the present upper limits on these processes.Comment: UMDHEP 94-30, 14 pages, TeX file, (some new references added
Canonical formulation of self-gravitating spinning-object systems
Based on the Arnowitt-Deser-Misner (ADM) canonical formulation of general
relativity, a canonical formulation of gravitationally interacting classical
spinning-object systems is given to linear order in spin. The constructed
position, linear momentum and spin variables fulfill standard Poisson bracket
relations. A spatially symmetric time gauge for the tetrad field is introduced.
The achieved formulation is of fully reduced form without unresolved
constraints, supplementary, gauge, or coordinate conditions. The canonical
field momentum is not related to the extrinsic curvature of spacelike
hypersurfaces in standard ADM form. A new reduction of the tetrad degrees of
freedom to the Einstein form of the metric field is suggested.Comment: 6 pages. v2: extended version; identical to the published one. v3:
corrected misprints in (24) and (39); improved notation; added note regarding
a further reference
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