1,217 research outputs found
Fractal Holography: a geometric re-interpretation of cosmological large scale structure
The fractal dimension of large-scale galaxy clustering has been demonstrated
to be roughly from a wide range of redshift surveys. If correct,
this statistic is of interest for two main reasons: fractal scaling is an
implicit representation of information content, and also the value itself is a
geometric signature of area. It is proposed that the fractal distribution of
galaxies may thus be interpreted as a signature of holography (``fractal
holography''), providing more support for current theories of holographic
cosmologies. Implications for entropy bounds are addressed. In particular,
because of spatial scale invariance in the matter distribution, it is shown
that violations of the spherical entropy bound can be removed. This holographic
condition instead becomes a rigid constraint on the nature of the matter
density and distribution in the Universe. Inclusion of a dark matter
distribution is also discussed, based on theoretical considerations of possible
universal CDM density profiles.Comment: 13 pp, LaTeX. Revised version; to appear in JCA
Heavy Mineral Variability And Provenance Of The Virginia Inner Shelf And Lower Chesapeake Bay
The mineral composition of the 3- to 4-phi (0.125 to 0.063 mm) size fraction of 49 surficial grab samples,located north and south of the entrance to Chesapeake Bay and of 38 surficial samples, located in the bay mouth, was determined during this study. Although up to 17 minerals were identified, principal components analysis indicated that seven minerals accounted for 96 percent of the composition variance in the bay samples. By using Q-mode factor analysis, three mineral composition end-members (factors) were selected from the sample data and provided an adequate description of the spatial variation in heavy-mineral composition. The end members suggest possible mineral sources.https://scholarworks.wm.edu/vimsbooks/1105/thumbnail.jp
Entropy of gravitating systems: scaling laws versus radial profiles
Through the consideration of spherically symmetric gravitating systems
consisting of perfect fluids with linear equation of state constrained to be in
a finite volume, an account is given of the properties of entropy at conditions
in which it is no longer an extensive quantity (it does not scale with system's
size). To accomplish this, the methods introduced by Oppenheim [1] to
characterize non-extensivity are used, suitably generalized to the case of
gravitating systems subject to an external pressure. In particular when, far
from the system's Schwarzschild limit, both area scaling for conventional
entropy and inverse radius law for the temperature set in (i.e. the same
properties of the corresponding black hole thermodynamical quantities), the
entropy profile is found to behave like 1/r, being r the area radius inside the
system. In such circumstances thus entropy heavily resides in internal layers,
in opposition to what happens when area scaling is gained while approaching the
Schwarzschild mass, in which case conventional entropy lies at the surface of
the system. The information content of these systems, even if it globally
scales like the area, is then stored in the whole volume, instead of packed on
the boundary.Comment: 16 pages, 11 figures. v2: addition of some references; the stability
of equilibrium configurations is readdresse
A finite cutoff on the string worldsheet?
D-brane backgrounds are specified in closed string theories by holes with
appropriate mixed Dirichlet and Neumann boundary conditions on the string
worldsheet. As presently stated, the prescription defining D-brane backgrounds
is such that the Einstein equation is not equivalent to the condition for scale
invariance on the string worldsheet. A modified D-brane prescription is found,
that leads to the desired equivalence, while preserving all known D-brane lore.
A possible interpretation is that the worldsheet cutoff is finite. Possible
connections to recent work of Maldacena and Strominger, and Gopakumar and Vafa
are suggested.Comment: 7 pages, RevTex; v2: typos corrected, superstring calculation
included, discussion expanded - to be published in Phys.Rev.
Heavy Mineral Concentrations In Sediments Of The Virginia Inner Continental Shelf
The Virginia Division of Mineral Resources and the Virginia Institute of Marine Science investigated the occurrence of heavy minerals in the offshore sediments of Virginia. We began the project because earlier reconnaissance studies reported high heavy-mineral concentrations from several samples collected off the Eastern Shore of Virginia. Our work confirms the previously reported mineral values and locates additional high concentrations up to 20 nautical miles offshore. Furthermore, we show that potentially economic mineral values are not restricted no surficial sediments, but also are found in the upper 15 to 20 feet of inner continental shelf sediments. Several core samples indicate that potential economic values of heavy minerals are clustered offshore of Hog Island, Smith Island, Virginia Beach, and False Cape. These areas are likely targets for resource assessment studies of heavy minerals and construction or beach nourishment sand. The high heavy-mineral concentrations suggest that further investigations are warranted.https://scholarworks.wm.edu/vimsbooks/1104/thumbnail.jp
Back Reaction of Hawking Radiation on Black Hole Geometry
We propose a model for the geometry of a dynamical spherical shell in which
the metric is asymptotically Schwarzschild, but deviates from Ricci-flatness in
a finite neighbourhood of the shell. Hence, the geometry corresponds to a
`hairy' black hole, with the hair originating on the shell. The metric is
regular for an infalling shell, but it bifurcates, leading to two disconnected
Schwarzschild-like spacetime geometries. The shell is interpreted as either
collapsing matter or as Hawking radiation, depending on whether or not the
shell is infalling or outgoing. In this model, the Hawking radiation results
from tunnelling between the two geometries. Using this model, the back reaction
correction from Hawking radiation is calculated.Comment: Latex file, 15 pages, 4 figures enclosed, uses eps
Hologrphy and holographic dark energy model
The holographic principle is used to discuss the holographic dark energy
model. We find that the Bekenstein-Hawking entropy bound is far from saturation
under certain conditions. A more general constraint on the parameter of the
holographic dark energy model is also derived.Comment: no figures, use revtex, v2: use iop style, some typos corrected and
references updated, will appear in CQ
Brane Boxes, Anomalies, Bending and Tadpoles
Certain classes of chiral four-dimensional gauge theories may be obtained as
the worldvolume theories of D5-branes suspended between networks of NS5-branes,
the so-called brane box models. In this paper, we derive the stringy
consistency conditions placed on these models, and show that they are
equivalent to anomaly cancellation of the gauge theories. We derive these
conditions in the orbifold theories which are T-dual to the elliptic brane box
models. Specifically, we show that the expression for tadpoles for unphysical
twisted Ramond-Ramond 4-form fields in the orbifold theory are proportional to
the gauge anomalies of the brane box theory. Thus string consistency is
equivalent to worldvolume gauge anomaly cancellation. Furthermore, we find
additional cylinder amplitudes which give the -functions of the gauge
theory. We show how these correspond to bending of the NS-branes in the brane
box theory.Comment: 14 pages, 3 epsf figures. Minor changes, references adde
Magnetic Wormholes and Vertex Operators
We consider wormhole solutions in Euclidean dimensions. A duality
transformation is introduced to derive a new action from magnetic wormhole
action of Gupta, Hughes, Preskill and Wise. The classical solution is
presented. The vertex operators corresponding to the wormhole are derived.
Conformally coupled scalars and spinors are considered in the wormhole
background and the vertex operators are computed. ( To be published in Phys.
Rev. D15)Comment: 18 pages of RevTex, preprint IP/BBSR/94-2
Singularities of -fold integrals of the Ising class and the theory of elliptic curves
We introduce some multiple integrals that are expected to have the same
singularities as the singularities of the -particle contributions
to the susceptibility of the square lattice Ising model. We find
the Fuchsian linear differential equation satisfied by these multiple integrals
for and only modulo some primes for and , thus
providing a large set of (possible) new singularities of the . We
discuss the singularity structure for these multiple integrals by solving the
Landau conditions. We find that the singularities of the associated ODEs
identify (up to ) with the leading pinch Landau singularities. The second
remarkable obtained feature is that the singularities of the ODEs associated
with the multiple integrals reduce to the singularities of the ODEs associated
with a {\em finite number of one dimensional integrals}. Among the
singularities found, we underline the fact that the quadratic polynomial
condition , that occurs in the linear differential equation
of , actually corresponds to a remarkable property of selected
elliptic curves, namely the occurrence of complex multiplication. The
interpretation of complex multiplication for elliptic curves as complex fixed
points of the selected generators of the renormalization group, namely
isogenies of elliptic curves, is sketched. Most of the other singularities
occurring in our multiple integrals are not related to complex multiplication
situations, suggesting an interpretation in terms of (motivic) mathematical
structures beyond the theory of elliptic curves.Comment: 39 pages, 7 figure
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