17,604 research outputs found
Hawking radiation from decoherence
It is argued that the thermal nature of Hawking radiation arises solely due
to decoherence. Thereby any information-loss paradox is avoided because for
closed systems pure states remain pure. The discussion is performed for a
massless scalar field in the background of a Schwarzschild black hole, but the
arguments should hold in general. The result is also compared to and contrasted
with the situation in inflationary cosmology.Comment: 6 pages, to appear in Class. Quantum Gra
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
Does Positronium Form in the Universe ?
Positronium (the bound state of electron and positron) has been thought to be
formed after proton decay (yr) through collisional recombination and
then decays by pair annihilation, thereby changing the matter content of the
universe. We revisit the issue of the formation of positronium in the long-term
future of the universe in light of recent indication that the universe is
dominated by dark energy and dark matter. We find that if the equation of state
of dark energy is less than -1/3 (including the cosmological constant
), then the formation of positronium would not be possible, while it is
possible through bound-bound transitions for -1/3\siml w\siml-0.2, or through
collisional recombination for w\simg-0.2. The radiation from \epm pair
annihilation cannot dominate over \epm, while that from proton decay will
dominate over baryon and \epm for a while but not over dark matter.Comment: 13 pages, to appear in JCA
Unifying Parsimonious Tree Reconciliation
Evolution is a process that is influenced by various environmental factors,
e.g. the interactions between different species, genes, and biogeographical
properties. Hence, it is interesting to study the combined evolutionary history
of multiple species, their genes, and the environment they live in. A common
approach to address this research problem is to describe each individual
evolution as a phylogenetic tree and construct a tree reconciliation which is
parsimonious with respect to a given event model. Unfortunately, most of the
previous approaches are designed only either for host-parasite systems, for
gene tree/species tree reconciliation, or biogeography. Hence, a method is
desirable, which addresses the general problem of mapping phylogenetic trees
and covering all varieties of coevolving systems, including e.g., predator-prey
and symbiotic relationships. To overcome this gap, we introduce a generalized
cophylogenetic event model considering the combinatorial complete set of local
coevolutionary events. We give a dynamic programming based heuristic for
solving the maximum parsimony reconciliation problem in time O(n^2), for two
phylogenies each with at most n leaves. Furthermore, we present an exact
branch-and-bound algorithm which uses the results from the dynamic programming
heuristic for discarding partial reconciliations. The approach has been
implemented as a Java application which is freely available from
http://pacosy.informatik.uni-leipzig.de/coresym.Comment: Peer-reviewed and presented as part of the 13th Workshop on
Algorithms in Bioinformatics (WABI2013
On arithmetic detection of grey pulses with application to Hawking radiation
Micron-sized black holes do not necessarily have a constant horizon
temperature distribution. The black hole remote-sensing problem means to find
out the `surface' temperature distribution of a small black hole from the
spectral measurement of its (Hawking) grey pulse. This problem has been
previously considered by Rosu, who used Chen's modified Moebius inverse
transform. Here, we hint on a Ramanujan generalization of Chen's modified
Moebius inverse transform that may be considered as a special wavelet
processing of the remote-sensed grey signal coming from a black hole or any
other distant grey sourceComment: 5 pages, published versio
Intersubband magnetophonon resonances in quantum cascade structures
We report on our magnetotransport measurements of GaAs/GaAlAs quantum cascade
structures in a magnetic field of up to 62 T. We observe novel quantum
oscillations in tunneling current that are periodic in reciprocal magnetic
field. We explain these oscillations as intersubband magnetophonon resonance
due to electron relaxation by emission of either single optical or acoustic
phonons. Our work also provides a non-optical in situ measurement of
intersubband separations in quantum cascade structures.Comment: 5 pages, 4 figure
Information Flow in Entangled Quantum Systems
All information in quantum systems is, notwithstanding Bell's theorem,
localised. Measuring or otherwise interacting with a quantum system S has no
effect on distant systems from which S is dynamically isolated, even if they
are entangled with S. Using the Heisenberg picture to analyse quantum
information processing makes this locality explicit, and reveals that under
some circumstances (in particular, in Einstein-Podolski-Rosen experiments and
in quantum teleportation) quantum information is transmitted through
'classical' (i.e. decoherent) information channels.Comment: PostScript version now available:
http://www.qubit.org/people/patrickh/Papers/InformationFlow.p
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