4,427 research outputs found
Loop Model with Generalized Fugacity in Three Dimensions
A statistical model of loops on the three-dimensional lattice is proposed and
is investigated. It is O(n)-type but has loop fugacity that depends on global
three-dimensional shapes of loops in a particular fashion. It is shown that,
despite this non-locality and the dimensionality, a layer-to-layer transfer
matrix can be constructed as a product of local vertex weights for infinitely
many points in the parameter space. Using this transfer matrix, the site
entropy is estimated numerically in the fully packed limit.Comment: 16pages, 4 eps figures, (v2) typos and Table 3 corrected. Refs added,
(v3) an error in an explanation of fig.2 corrected. Refs added. (v4) Changes
in the presentatio
Almost Ideal Clocks in Quantum Cosmology: A Brief Derivation of Time
A formalism for quantizing time reparametrization invariant dynamics is
considered and applied to systems which contain an `almost ideal clock.'
Previously, this formalism was successfully applied to the Bianchi models and,
while it contains no fundamental notion of `time' or `evolution,' the approach
does contain a notion of correlations. Using correlations with the almost ideal
clock to introduce a notion of time, the work below derives the complete
formalism of external time quantum mechanics. The limit of an ideal clock is
found to be closely associated with the Klein-Gordon inner product and the
Newton-Wigner formalism and, in addition, this limit is shown to fail for a
clock that measures metric-defined proper time near a singularity in Bianchi
models.Comment: 16 pages ReVTeX (35 preprint pages
Native Hawaiian Grandparents: Exploring Benefits and Challenges in the Caregiving Experience
Background: Increasingly, U.S. grandparents are raising their grandchildren. In Hawai‘i, 12% of Native Hawaiian grandparents live with grandchildren, compared to 7% of grandparents in all races combined in the state, and to 3.6% of grandparents in the total U.S. Although strong family-centric cultural values may provide Native Hawaiian grandparents with caregiving benefits, a generally poor health profile suggests they may also face challenges in this role. In this study, we talked to Native Hawaiian grandparents raising grandchildren (GRG) about the benefits and challenges of their caregiving experiences. Method: Three focus groups were conducted with Native Hawaiian grandparents (n=33) in Hawai‘i who were 55 years of age or older and caregivers to their grandchildren. Findings: The most prevalent themes voiced by grandparents spoke of the benefits of being a grandparent caregiver (the greatest being the experience of mutual, unconditional love) and the enjoyment of passing on “life lessons” to their grandchildren. Grandparents identified concrete examples of what they provided to grandchildren and also spoke of their role in transmission of Native Hawaiian cultural values, practices, and stories to their grandchildren. A number of challenges pertaining to grandparent caregiving were identified along with needed services—respite care, financial assistance, children’s programs, and information on grandparent legal rights. Despite these challenges, grandparents preferred to seek help from extended family rather than from formal supports. Our results support previous research on a number of universal GRG needs and services (i.e., legal rights of GRG) but also suggest potential directions to meeting the needs of Native Hawaiian GRG that are responsive to indigenous cultural values and preferences. Given the number of unmet needs expressed, further research is needed to design interventions for this population of grandparents raising grandchildren
CBR Temperature Fluctuations Induced by Gravitational Waves in a Spatially-Closed Inflationary Universe
Primordial gravitational waves are created during the de Sitter phase of an
exponentially-expanding (inflationary) universe, due to quantum zero-point
vacuum fluctuations. These waves produce fluctuations in the temperature of the
Cosmic Background Radiation (CBR). We calculate the multipole moments of the
correlation function for these temperature fluctuations in a spatially-closed
Friedman-Robertson-Walker (FRW) cosmological model. The results are compared to
the corresponding multipoles in the spatially-flat case. The differences are
small unless the density parameter today, , is greater than 2.
(Submitted to Physical Review D).Comment: 18 pages of RevTex + 3 uuencoded postscript figure
Sudden drop of fractal dimension of electromagnetic emissions recorded prior to significant earthquake
The variation of fractal dimension and entropy during a damage evolution
process, especially approaching critical failure, has been recently
investigated. A sudden drop of fractal dimension has been proposed as a
quantitative indicator of damage localization or a likely precursor of an
impending catastrophic failure. In this contribution, electromagnetic emissions
recorded prior to significant earthquake are analysed to investigate whether
they also present such sudden fractal dimension and entropy drops as the main
catastrophic event is approaching. The pre-earthquake electromagnetic time
series analysis results reveal a good agreement to the theoretically expected
ones indicating that the critical fracture is approaching
Weak gravity in DGP braneworld model
We analyze the weak gravity in the braneworld model proposed by
Dvali-Gabadadze-Porrati, in which the unperturbed background spacetime is given
by five dimensional Minkowski bulk with a brane which has the induced Einstein
Hilbert term. This model has a critical length scale . Naively, we expect
that the four dimensional general relativity (4D GR) is approximately recovered
at the scale below . However, the simple linear perturbation does not work
in this regime. Only recently the mechanism to recover 4D GR was clarified
under the restriction to spherically symmetric configurations, and the leading
correction to 4D GR was derived. Here, we develop an alternative formulation
which can handle more general perturbations. We also generalize the model by
adding bulk cosmological constant and the brane tension.Comment: 7 pages, 1 figure, references adde
Scalar radiation emitted from a source rotating around a black hole
We analyze the scalar radiation emitted from a source rotating around a
Schwarzschild black hole using the framework of quantum field theory at the
tree level. We show that for relativistic circular orbits the emitted power is
about 20% to 30% smaller than what would be obtained in Minkowski spacetime. We
also show that most of the emitted energy escapes to infinity. Our formalism
can readily be adapted to investigate similar processes.Comment: 19 pages (REVTEX), 5 figures, title slightly changed, extra
demonstration and minor improvements included. To appear in Class. Quant.
Gra
Random-cluster representation of the Blume-Capel model
The so-called diluted-random-cluster model may be viewed as a random-cluster
representation of the Blume--Capel model. It has three parameters, a vertex
parameter , an edge parameter , and a cluster weighting factor .
Stochastic comparisons of measures are developed for the `vertex marginal' when
, and the `edge marginal' when q\in[1,\oo). Taken in conjunction
with arguments used earlier for the random-cluster model, these permit a
rigorous study of part of the phase diagram of the Blume--Capel model
The Fermion Self-Energy during Inflation
We compute the one loop fermion self-energy for massless Dirac + Einstein in
the presence of a locally de Sitter background. We employ dimensional
regularization and obtain a fully renormalized result by absorbing all
divergences with BPHZ counterterms. An interesting technical aspect of this
computation is the need for a noninvariant counterterm owing to the breaking of
de Sitter invariance by our gauge condition. Our result can be used in the
quantum-corrected Dirac equation to search for inflation-enhanced quantum
effects from gravitons, analogous to those which have been found for massless,
minimally coupled scalars.Comment: 63 pages, 3 figures (uses axodraw.sty), LaTeX 2epsilon. Revised
version (to appear in Classical and Quantum Gravity) corrects some typoes and
contains some new reference
Quantum Aspects of Massive Gravity II: Non-Pauli-Fierz Theory
We investigate the non-Pauli-Fierz(nPF) theory, a linearized massive gravity
with a generic graviton mass term, which has been ignored due to a ghost in its
spectrum and the resultant loss of unitarity. We first show that it is possible
to use the Lee-Wick mechanism, a unitarization through the decay of a ghost, in
order to handle the sixth mode ghost of nPF, and then check for the quantum
consistency. Once proven to be consistent, nPF could become a viable candidate
for a large distance modification of gravity, because it naturally solves the
intrinsic problems that most dark energy/modified gravity models suffer from:
It smoothly converges to general relativity at short distances, and the small
graviton mass necessary to modify gravity at large scales can be stable under
the radiative corrections from the minimal gravity-to-matter coupling.Comment: 1+16pp, accepted for JHE
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