100,700 research outputs found
Existence and uniqueness theorems for massless fields on a class of spacetimes with closed timelike curves
We study the massless scalar field on asymptotically flat spacetimes with
closed timelike curves (CTC's), in which all future-directed CTC's traverse one
end of a handle (wormhole) and emerge from the other end at an earlier time.
For a class of static geometries of this type, and for smooth initial data with
all derivatives in on {\cI}^{-}, we prove existence of smooth solutions
which are regular at null and spatial infinity (have finite energy and finite
-norm) and have the given initial data on \cI^-. A restricted uniqueness
theorem is obtained, applying to solutions that fall off in time at any fixed
spatial position. For a complementary class of spacetimes in which CTC's are
confined to a compact region, we show that when solutions exist they are unique
in regions exterior to the CTC's. (We believe that more stringent uniqueness
theorems hold, and that the present limitations are our own.) An extension of
these results to Maxwell fields and massless spinor fields is sketched.
Finally, we discuss a conjecture that the Cauchy problem for free fields is
well defined in the presence of CTC's whenever the problem is well-posed in the
geometric-optics limit. We provide some evidence in support of this conjecture,
and we present counterexamples that show that neither existence nor uniqueness
is guaranteed under weaker conditions. In particular, both existence and
uniqueness can fail in smooth, asymptotically flat spacetimes with a compact
nonchronal region.Comment: 47 pages, Revtex, 7 figures (available upon request
Putting the Horse Before the Cart: The Influence of Trigger Events on Justice Perceptions and Work Attitudes
To date very little research on organizational justice and work attitudes has focused on what starts the process that leads to these perceptions. A considerable amount of organizational research is focused on the end result (e.g., employeesâ perceptions, attitudes, or behaviors), which can become difficult to effectively manage or change after-the-fact in a timely or productive manner (Tekleab et al., 2005). In this paper, two studies are conducted that explore a variety of events employees might notice and how they influence workplace outcomes. Study One explores 16 trigger events from prior research and surveys employees in a manufacturing organization about the events, and identifying 24 additional events. Study Two examines relationships between the trigger events and outcomes of pay and job satisfaction, organizational commitment, and intent to leave, using organizational justice as a mechanism for sensemaking. Results from Study Two show that trigger events significantly predicted all four workplace attitudes. Procedural justice was significantly related to all dependent variables, interactional justice was significantly related only to job satisfaction and intention to leave, marginally unrelated to pay satisfaction, and unrelated to organizational commitment. Distributive justice was significantly related to job satisfaction, intention to leave, and pay satisfaction, but not organizational commitment. Seven of the 48 interaction terms examined were significant. Limitations and implications for future research are discussed
A parabolic free boundary problem with Bernoulli type condition on the free boundary
Consider the parabolic free boundary problem For a
realistic class of solutions, containing for example {\em all} limits of the
singular perturbation problem we prove that one-sided
flatness of the free boundary implies regularity.
In particular, we show that the topological free boundary
can be decomposed into an {\em open} regular set (relative to
) which is locally a surface with H\"older-continuous space
normal, and a closed singular set.
Our result extends the main theorem in the paper by H.W. Alt-L.A. Caffarelli
(1981) to more general solutions as well as the time-dependent case. Our proof
uses methods developed in H.W. Alt-L.A. Caffarelli (1981), however we replace
the core of that paper, which relies on non-positive mean curvature at singular
points, by an argument based on scaling discrepancies, which promises to be
applicable to more general free boundary or free discontinuity problems
Braggoriton--Excitation in Photonic Crystal Infiltrated with Polarizable Medium
Light propagation in a photonic crystal infiltrated with polarizable
molecules is considered. We demonstrate that the interplay between the spatial
dispersion caused by Bragg diffraction and polaritonic frequency dispersion
gives rise to novel propagating excitations, or braggoritons, with intragap
frequencies. We derive the braggoriton dispersion relation and show that it is
governed by two parameters, namely, the strength of light-matter interaction
and detuning between the Bragg frequency and that of the infiltrated molecules.
We also study defect-induced states when the photonic band gap is divided into
two subgaps by the braggoritonic branches and find that each defect creates two
intragap localized states inside each subgap.Comment: LaTeX, 8 pages, 5 figure
Multiphoton localization and propagating quantum gap solitons in a frequency gap medium
The many-particle spectrum of an isotropic frequency gap medium doped with
impurity resonance atoms is studied using the Bethe ansatz technique. The
spectrum is shown to contain pairs of quantum correlated ``gap excitations''
and their heavy bound complexes (``gap solitons''), enabling the propagation of
quantum information within the classically forbidden gap. In addition,
multiparticle localization of the radiation and the medium polarization occurs
when such a gap soliton is pinned to the impurity atom.Comment: 8 pages, RevTEX, to appear in Phys. Rev. Let
Higher Dimensional Lattice Chains and Delannoy Numbers
Fix nonnegative integers n1 , . . ., nd, and let L denote the lattice of points (a1 , . . ., ad) â â€d that satisfy 0 †ai †ni for 1 †i †d. Let L be partially ordered by the usual dominance ordering. In this paper we use elementary combinatorial arguments to derive new expressions for the number of chains and the number of Delannoy paths in L. Setting ni = n (for all i) in these expressions yields a new proof of a recent result of Duichi and Sulanke [9] relating the total number of chains to the central Delannoy numbers. We also give a novel derivation of the generating functions for these numbers in arbitrary dimension
The experiences of women with polycystic ovary syndrome on a very low-calorie diet
The research was funded by an educational grant from LighterLife. Broom was the Medical Director for LighterLife at the time of the research. Johnson is the Head of Nutrition and Research at LighterLife. The authors report no other conflicts of interest in this work.Peer reviewedPublisher PD
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