1,004 research outputs found
Quantum Effective Action in Spacetimes with Branes and Boundaries: Diffeomorphism Invariance
We construct a gauge-fixing procedure in the path integral for gravitational
models with branes and boundaries. This procedure incorporates a set of gauge
conditions which gauge away effectively decoupled diffeomorphisms acting in the
-dimensional bulk and on the -dimensional brane. The corresponding
gauge-fixing factor in the path integral factorizes as a product of the bulk
and brane (surface-theory) factors. This factorization underlies a special bulk
wavefunction representation of the brane effective action. We develop the
semiclassical expansion for this action and explicitly derive it in the
one-loop approximation. The one-loop brane effective action can be decomposed
into the sum of the gauge-fixed bulk contribution and the contribution of the
pseudodifferential operator of the brane-to-brane propagation of quantum
gravitational perturbations. The gauge dependence of these contributions is
analyzed by the method of Ward identities. By the recently suggested method of
the Neumann-Dirichlet reduction the bulk propagator in the semiclassical
expansion is converted to the Dirichlet boundary conditions preferable from the
calculational viewpoint.Comment: 37 pages, LaTe
Pressurant requirements for discharge of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank under both static and slosh conditions
Pressurized expulsion tests were conducted to determine the effect of various physical parameters on the pressurant gas (methane, helium, hydrogen, and nitrogen) requirements during the expulsion of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank and to compare results with those predicted by an analytical program. Also studied were the effects on methane, helium, and hydrogen pressurant requirements of various slosh excitation frequencies and amplitudes, both with and without slosh suppressing baffles in the tank. The experimental results when using gaseous methane, helium, and hydrogen show that the predictions of the analytical program agreed well with the actual pressurant requirements for static tank expulsions. The analytical program could not be used for gaseous nitrogen expulsions because of the large quantities of nitrogen which can dissolve in liquid methane. Under slosh conditions, a pronounced increase in gaseous methane requirements was observed relative to results obtained for the static tank expulsions. Slight decreases in the helium and hydrogen requirements were noted under similar test conditions
Quantum Effective Action in Spacetimes with Branes and Boundaries
We construct quantum effective action in spacetime with branes/boundaries.
This construction is based on the reduction of the underlying Neumann type
boundary value problem for the propagator of the theory to that of the much
more manageable Dirichlet problem. In its turn, this reduction follows from the
recently suggested Neumann-Dirichlet duality which we extend beyond the tree
level approximation. In the one-loop approximation this duality suggests that
the functional determinant of the differential operator subject to Neumann
boundary conditions in the bulk factorizes into the product of its Dirichlet
counterpart and the functional determinant of a special operator on the brane
-- the inverse of the brane-to-brane propagator. As a byproduct of this
relation we suggest a new method for surface terms of the heat kernel
expansion. This method allows one to circumvent well-known difficulties in heat
kernel theory on manifolds with boundaries for a wide class of generalized
Neumann boundary conditions. In particular, we easily recover several lowest
order surface terms in the case of Robin and oblique boundary conditions. We
briefly discuss multi-loop applications of the suggested Dirichlet reduction
and the prospects of constructing the universal background field method for
systems with branes/boundaries, analogous to the Schwinger-DeWitt technique.Comment: LaTeX, 25 pages, final version, to appear in Phys. Rev.
A two-crop beetle update
Feeding by bean leaf beetles and corn flea beetles has been reported in Iowa fields. These beetles are very noticeable on emerging soybean and corn, respectively, which leads to questions about needs for pesticide treatment
Higher order relations in Fedosov supermanifolds
Higher order relations existing in normal coordinates between affine
extensions of the curvature tensor and basic objects for any Fedosov
supermanifolds are derived. Representation of these relations in general
coordinates is discussed.Comment: 11 LaTex pages, no figure
One-Loop Effective Action on the Four-Ball
This paper applies -function regularization to evaluate the 1-loop
effective action for scalar field theories and Euclidean Maxwell theory in the
presence of boundaries. After a comparison of two techniques developed in the
recent literature, vacuum Maxwell theory is studied and the contribution of all
perturbative modes to is derived: transverse, longitudinal and
normal modes of the electromagnetic potential, jointly with ghost modes. The
analysis is performed on imposing magnetic boundary conditions, when the
Faddeev-Popov Euclidean action contains the particular gauge-averaging term
which leads to a complete decoupling of all perturbative modes. It is shown
that there is no cancellation of the contributions to resulting
from longitudinal, normal and ghost modes.Comment: 25 pages, plain Te
Quantum gravitational measure for three-geometries
The gravitational measure on an arbitrary topological three-manifold is
constructed. The nontrivial dependence of the measure on the conformal factor
is discussed. We show that only in the case of a compact manifold with boundary
the measure acquires a nontrivial dependence on the conformal factor which is
given by the Liouville action. A nontrivial Jacobian (the divergent part of it)
generates the Einstein-Hilbert action. The Hartle-Hawking wave function of
Universe is given in terms of the Liouville action. In the gaussian
approximation to the Wheeler-DeWitt equation this result was earlier derived by
Banks et al. Possible connection with the Chern-Simons gravity is also
discussed.Comment: 16 pages, TeX. This is the original, preprint version of the paper
that with some modifications was published i
A Comparative Study of Laplacians and Schroedinger-Lichnerowicz-Weitzenboeck Identities in Riemannian and Antisymplectic Geometry
We introduce an antisymplectic Dirac operator and antisymplectic gamma
matrices. We explore similarities between, on one hand, the
Schroedinger-Lichnerowicz formula for spinor bundles in Riemannian spin
geometry, which contains a zeroth-order term proportional to the Levi-Civita
scalar curvature, and, on the other hand, the nilpotent, Grassmann-odd,
second-order \Delta operator in antisymplectic geometry, which in general has a
zeroth-order term proportional to the odd scalar curvature of an arbitrary
antisymplectic and torsionfree connection that is compatible with the measure
density. Finally, we discuss the close relationship with the two-loop scalar
curvature term in the quantum Hamiltonian for a particle in a curved Riemannian
space.Comment: 55 pages, LaTeX. v2: Subsection 3.10 expanded. v3: Reference added.
v4: Published versio
Wheeler-DeWitt equation and Feynman diagrams
We present a systematic expansion of all constraint equations in canonical
quantum gravity up to the order of the inverse Planck mass squared. It is
demonstrated that this method generates the conventional Feynman diagrammatic
technique involving graviton loops and vertices. It also reveals explicitly the
back reaction effects of quantized matter and graviton vacuum polarization.
This provides an explicit correspondence between the frameworks of canonical
and covariant quantum gravity in the semiclassical limit.Comment: 35 pages, LATEX, 1 figur
Dimensional regularization of nonlinear sigma models on a finite time interval
We extend dimensional regularization to the case of compact spaces. Contrary
to previous regularization schemes employed for nonlinear sigma models on a
finite time interval (``quantum mechanical path integrals in curved space'')
dimensional regularization requires only a covariant finite two-loop
counterterm. This counterterm is nonvanishing and given by R/8.Comment: 9 pages, 7 figures, LaTeX, minor changes in text and reference
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