14,040 research outputs found
The Anisotropy in the Cosmic Microwave Background At Degree Angular Scales
We detect anisotropy in the cosmic microwave background (CMB) at degree
angular scales and confirm a previous detection reported by Wollack et al.
(1993). The root-mean-squared amplitude of the fluctuations is K. This may be expressed as the square root of the angular power spectrum
in a band of multipoles between . We find K. The measured spectral
index of the fluctuations is consistent with zero, the value expected for the
CMB. The spectral index corresponding to Galactic free-free emission, the most
likely foreground contaminant, is rejected at approximately .
The analysis is based on three independent data sets. The first, taken in
1993, spans the 26 - 36 GHz frequency range with three frequency bands; the
second was taken with the same radiometer as the first but during an
independent observing campaign in 1994; and the third, also take in 1994, spans
the 36-46 GHz range in three bands. For each telescope position and radiometer
channel, the drifts in the instrument offset are K/day over a period
of one month. The dependence of the inferred anisotropy on the calibration and
data editing is addressed.Comment: 16 pages, 2 figures. Saskatoon 1993/1994 combined analysi
Nonconidiation in the new homothallic species, Neurospora terricola
Nonconidiation in the new homothallic species, Neurospora terricol
Observation of infinite-range intensity correlations above, at and below the 3D Anderson localization transition
We investigate long-range intensity correlations on both sides of the
Anderson transition of classical waves in a three-dimensional (3D) disordered
material. Our ultrasonic experiments are designed to unambiguously detect a
recently predicted infinite-range C0 contribution, due to local density of
states fluctuations near the source. We find that these C0 correlations, in
addition to C2 and C3 contributions, are significantly enhanced near mobility
edges. Separate measurements of the inverse participation ratio reveal a link
between C0 and the anomalous dimension \Delta_2, implying that C0 may also be
used to explore the critical regime of the Anderson transition.Comment: 13 pages, 11 figures (main text plus supplemental information).
Updated version includes an improved introductory paragraph, minor text
revisions, a revised title and additional supplemental information on the
experimental detail
Black Hole Motion in Entropic Reformulation of General Relativity
We consider a system of black holes -- a simplest substitute of a system of
point particles in the mechanics of general relativity -- and try to describe
their motion with the help of entropic action: a sum of the areas of black hole
horizons. We demonstrate that such description is indeed consistent with the
Newton's laws of motion and gravity, modulo numerical coefficients, which
coincide but seem different from unity. Since a large part of the modern
discussion of entropic reformulation of general relativity is actually based on
dimensional considerations, for making a next step it is crucially important to
modify the argument, so that these dimensionless parameters acquire correct
values.Comment: 6 page
Do Evaporating Black Holes Form Photospheres?
Several authors, most notably Heckler, have claimed that the observable
Hawking emission from a microscopic black hole is significantly modified by the
formation of a photosphere around the black hole due to QED or QCD interactions
between the emitted particles. In this paper we analyze these claims and
identify a number of physical and geometrical effects which invalidate these
scenarios. We point out two key problems. First, the interacting particles must
be causally connected to interact, and this condition is satisfied by only a
small fraction of the emitted particles close to the black hole. Second, a
scattered particle requires a distance ~ E/m_e^2 for completing each
bremsstrahlung interaction, with the consequence that it is improbable for
there to be more than one complete bremsstrahlung interaction per particle near
the black hole. These two effects have not been included in previous analyses.
We conclude that the emitted particles do not interact sufficiently to form a
QED photosphere. Similar arguments apply in the QCD case and prevent a QCD
photosphere (chromosphere) from developing when the black hole temperature is
much greater than Lambda_QCD, the threshold for QCD particle emission.
Additional QCD phenomenological arguments rule out the development of a
chromosphere around black hole temperatures of order Lambda_QCD. In all cases,
the observational signatures of a cosmic or Galactic halo background of
primordial black holes or an individual black hole remain essentially those of
the standard Hawking model, with little change to the detection probability. We
also consider the possibility, as proposed by Belyanin et al. and D. Cline et
al., that plasma interactions between the emitted particles form a photosphere,
and we conclude that this scenario too is not supported.Comment: version published in Phys Rev D 78, 064043; 25 pages, 3 figures;
includes discussion on extending our analysis to TeV-scale,
higher-dimensional black hole
Perceptions of Body Size in Mothers and Their Young Children in the Galapagos Islands
Little specific information has been published about the health of people who live in the Galapagos Islands. As part of determining the status of the nutrition transition that may be occurring in the islands mothers of young children in the Galapagos perceptions of their child’s body size and therefore health status was evaluated along with actual body size
Rotating Black Holes in Higher Dimensions with a Cosmological Constant
We present the metric for a rotating black hole with a cosmological constant
and with arbitrary angular momenta in all higher dimensions. The metric is
given in both Kerr-Schild and Boyer-Lindquist form. In the Euclidean-signature
case, we also obtain smooth compact Einstein spaces on associated S^{D-2}
bundles over S^2, infinitely many for each odd D\ge 5. Applications to string
theory and M-theory are indicated.Comment: 8 pages, Latex. Short version, with more compact notation, of
hep-th/0404008. To appear in Phys. Rev. Let
Information in Black Hole Radiation
If black hole formation and evaporation can be described by an matrix,
information would be expected to come out in black hole radiation. An estimate
shows that it may come out initially so slowly, or else be so spread out, that
it would never show up in an analysis perturbative in , or in 1/N
for two-dimensional dilatonic black holes with a large number of minimally
coupled scalar fields.Comment: 12 pages, 1 PostScript figure, LaTeX, Alberta-Thy-24-93 (In response
to Phys. Rev. Lett. referees' comments, the connection between expansions in
inverse mass and in 1/N are spelled out, and a figure is added. An argument
against perturbatively predicting even late-time information is also
provided, as well as various minor changes.
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