2,204 research outputs found
On the area expectation values in area tensor Regge calculus in the Lorentzian domain
Wick rotation in area tensor Regge calculus is considered. The heuristical
expectation is confirmed that the Lorentzian quantum measure on a spacelike
area should coincide with the Euclidean measure at the same argument. The
consequence is validity of probabilistic interpretation of the Lorentzian
measure as well (on the real, i.e. spacelike areas).Comment: LaTeX, 7 pages, introduction and discussion given in more detail,
references adde
Physician-owned specialized facilities: focused factories or destructive competition?: a systematic review.
Multiple studies have investigated the business case of physician-owned specialized facilities (specialized hospitals and ambulatory surgery centers). However literature lacks integration. Building on the theoretical insights of disruptive innovation, a systematic review was conducted to assess the evidence base of these innovative delivery models. The Institute of Medicineâs quality framework (safe, effective, equitable, efficient, patient-centered and accessible care) was applied in order to evaluate the performance of such facilities. In addition the corresponding impact on full-service general hospitals was assessed. Database searches yielded 6,108 candidate articles of which 47 studies fulfilled the inclusion criteria. Overall the quality of the included studies was satisfactory. Our results show that little evidence exists in support of competitive advantages in favor of specialized facilities. Moreover even if competitive advantages exist, it is equally important to reflect on the corresponding impact on full service-general hospitals. The development of specialized facilities should therefore be monitored carefully
A Gravitational Effective Action on a Finite Triangulation
We construct a function of the edge-lengths of a triangulated surface whose
variation under a rescaling of all the edges that meet at a vertex is the
defect angle at that vertex. We interpret this function as a gravitational
effective action on the triangulation, and the variation as a trace anomaly.Comment: 5 pages; clarifications, acknowledgements, references adde
Unified Brane Gravity: Cosmological Dark Matter from Scale Dependent Newton Constant
We analyze, within the framework of unified brane gravity, the weak-field
perturbations caused by the presence of matter on a 3-brane. Although deviating
from the Randall-Sundrum approach, the masslessness of the graviton is still
preserved. In particular, the four-dimensional Newton force law is recovered,
but serendipitously, the corresponding Newton constant is shown to be
necessarily lower than the one which governs FRW cosmology. This has the
potential to puzzle out cosmological dark matter. A subsequent conjecture
concerning galactic dark matter follows.Comment: 6 pages, to be published in Phys. Rev.
Hierarchies of invariant spin models
In this paper we present classes of state sum models based on the recoupling
theory of angular momenta of SU(2) (and of its q-counterpart , q a
root of unity). Such classes are arranged in hierarchies depending on the
dimension d, and include all known closed models, i.e. the Ponzano-Regge state
sum and the Turaev-Viro invariant in dimension d=3, the Crane-Yetter invariant
in d=4. In general, the recoupling coefficient associated with a d-simplex
turns out to be a symbol, or its q-analog. Each of the
state sums can be further extended to compact triangulations of a PL-pair , where the triangulation of the
boundary manifold is not keeped fixed. In both cases we find out the algebraic
identities which translate complete sets of topological moves, thus showing
that all state sums are actually independent of the particular triangulation
chosen. Then, owing to Pachner's theorems, it turns out that classes of
PL-invariant models can be defined in any dimension d.Comment: 42 pages, 25 figure
Degeneracies when T=0 Two Body Interacting Matrix Elements are Set Equal to Zero : Talmi's method of calculating coefficients of fractional parentage to states forbidden by the Pauli principle
In a previous work we studied the effects of setting all two body T=0 matrix
elements to zero in shell model calculations for Ti (Sc) and
Ti. The results for Ti were surprisingly good despite the
severity of this approximation. In this approximation degeneracies arose in the
T=1/2 I= and states in Sc and the T=1/2
, , and in Sc. The T=0
, , , and states in Ti were degenerate as
well. The degeneracies can be explained by certain 6j symbols and 9j symbols
either vanishing or being equal as indeed they are. Previously we used Regge
symmetries of 6j symbols to explain these degeneracies. In this work a simpler
more physical method is used. This is Talmi's method of calculating
coefficients of fractional parentage for identical particles to states which
are forbidden by the Pauli principle. This is done for both one particle cfp to
handle 6j symbols and two particle cfp to handle 9j symbols. The states can be
classified by the dual quantum numbers ()
Entropy Count for Extremal Three-Dimensional Black Strings
We compute the entropy of extremal black strings in three dimensions, using
Strominger's approach to relate the Anti-de-Sitter near-horizon geometry and
the conformal field theory at the asymptotic infinity of this geometry. The
result is identical to the geometric Bekenstein-Hawking entropy. We further
discuss an embedding of three-dimensional black strings in
supergravity and demonstrate that the extremal strings preserve 1/4 of
supersymmetries.Comment: 14 pages, latex, 1 .ps figure, a comment and some references added,
as accepted for publication in Phys. Lett.
Gravity action on the rapidly varying metrics
We consider a four-dimensional simplicial complex and the minisuperspace
general relativity system described by the metric flat in the most part of the
interior of every 4-simplex with exception of a thin layer of thickness
along the every three-dimensional face where the metric
undergoes jump between the two 4-simplices sharing this face. At this jump would become discontinuity. Since, however, discontinuity of
the (induced on the face) metric is not allowed in general relativity, the
terms in the Einstein action tending to infinity at arise.
In the path integral approach, these terms lead to the pre-exponent factor with
\dfuns requiring that the induced on the faces metric be continuous, i. e. the
4-simplices fit on their common faces. The other part of the path integral
measure corresponds to the action being the sum of independent terms over the
4-simplices. Therefore this part of the path integral measure is the product of
independent measures over the 4-simplices. The result obtained is in accordance
with our previous one obtained from the symmetry considerations.Comment: 10 page
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