24,052 research outputs found
Causality in Time-Neutral Cosmologies
Gell-Mann and Hartle (GMH) have recently considered time-neutral cosmological
models in which the initial and final conditions are independently specified,
and several authors have investigated experimental tests of such models.
We point out here that GMH time-neutral models can allow superluminal
signalling, in the sense that it can be possible for observers in those
cosmologies, by detecting and exploiting regularities in the final state, to
construct devices which send and receive signals between space-like separated
points. In suitable cosmologies, any single superluminal message can be
transmitted with probability arbitrarily close to one by the use of redundant
signals. However, the outcome probabilities of quantum measurements generally
depend on precisely which past {\it and future} measurements take place. As the
transmission of any signal relies on quantum measurements, its transmission
probability is similarly context-dependent. As a result, the standard
superluminal signalling paradoxes do not apply. Despite their unusual features,
the models are internally consistent.
These results illustrate an interesting conceptual point. The standard view
of Minkowski causality is not an absolutely indispensable part of the
mathematical formalism of relativistic quantum theory. It is contingent on the
empirical observation that naturally occurring ensembles can be naturally
pre-selected but not post-selected.Comment: 5 pages, RevTeX. Published version -- minor typos correcte
Extension of the tridiagonal reduction (FEER) method for complex eigenvalue problems in NASTRAN
As in the case of real eigenvalue analysis, the eigensolutions closest to a selected point in the eigenspectrum were extracted from a reduced, symmetric, tridiagonal eigenmatrix whose order was much lower than that of the full size problem. The reduction process was effected automatically, and thus avoided the arbitrary lumping of masses and other physical quantities at selected grid points. The statement of the algebraic eigenvalue problem admitted mass, damping, and stiffness matrices which were unrestricted in character, i.e., they might be real, symmetric or nonsymmetric, singular or nonsingular
Almost Certain Escape from Black Holes
This paper examines how black holes might compute in light of recent models
of the black-hole final state. These models suggest that quantum information
can escape from the black hole by a process akin to teleportation. They require
a specific final state and restrictions on the interaction between the
collapsing matter and the incoming Hawking radiation for quantum information to
escape. This paper shows that for an arbitrary final state and for generic
interactions between matter and Hawking radiation, the quantum information
about how the hole was formed and the results of any computation performed by
the matter inside the hole escapes with fidelity exponentially close to 1.Comment: 9 Pages, Te
N K and Delta K states in the chiral SU(3) quark model
The isospin I=0 and I=1 kaon-nucleon , , , wave phase shifts are
studied in the chiral SU(3) quark model by solving the resonating group method
(RGM) equation. The calculated phase shifts for different partial waves are in
agreement with the experimental data. Furthermore, the structures of the
states with L=0, I=1 and I=2 are investigated. We find that the
interaction between and in the case of L=0, I=1 is attractive,
which is not like the situation of the system, where the -wave
interactions between and for both I=0 and I=1 are repulsive. Our
numerical results also show that when the model parameters are taken to be the
same as in our previous and scattering calculations, the
state with L=0 and I=1 is a weakly bound state with about 2 MeV binding energy,
while the one with I=2 is unbound in the present one-channel calculation.Comment: 14 pages, 6 figures. PRC70,064004(2004
On the extent and role of the small proteome in the parasitic eukaryote Trypanosoma brucei
Background: Although technical advances in genomics and proteomics research have yielded a better understanding of the coding capacity of a genome, one major challenge remaining is the identification of all expressed proteins, especially those less than 100 amino acids in length. Such information can be particularly relevant to human pathogens, such as Trypanosoma brucei, the causative agent of African trypanosomiasis, since it will provide further insight into the parasite biology and life cycle. Results: Starting with 993 T. brucei transcripts, previously shown by RNA-Sequencing not to coincide with annotated coding sequences (CDS), homology searches revealed that 173 predicted short open reading frames in these transcripts are conserved across kinetoplastids with 13 also conserved in representative eukaryotes. Mining mass spectrometry data sets revealed 42 transcripts encoding at least one matching peptide. RNAi-induced down-regulation of these 42 transcripts revealed seven to be essential in insect-form trypanosomes with two also required for the bloodstream life cycle stage. To validate the specificity of the RNAi results, each lethal phenotype was rescued by co-expressing an RNAi-resistant construct of each corresponding CDS. These previously non-annotated essential small proteins localized to a variety of cell compartments, including the cell surface, mitochondria, nucleus and cytoplasm, inferring the diverse biological roles they are likely to play in T. brucei. We also provide evidence that one of these small proteins is required for replicating the kinetoplast (mitochondrial) DNA. Conclusions: Our studies highlight the presence and significance of small proteins in a protist and expose potential new targets to block the survival of trypanosomes in the insect vector and/or the mammalian host
Reactor antineutrino spectra and their application to antineutrino-induced reactions. II
The antineutrino and electron spectra associated with various nuclear fuels are calculated. While there are substantial differences between the spectra of different uranium and plutonium isotopes, the dependence on the energy and flux of the fission-inducing neutrons is very weak. The resulting spectra can be used for the calculation of the antineutrino and electron spectra of an arbitrary nuclear reactor at various stages of its refueling cycle. The sources of uncertainties in the spectrum are identified and analyzed in detail. The exposure time dependence of the spectrum is also discussed. The averaged cross sections of the inverse neutron β decay, weak charged and neutral-current-induced deuteron disintegration, and the antineutrino-electron scattering are then evaluated using the resulting νĚ
_e spectra.
[RADIOACTIVITY, FISSION 235U, 238U, (^239)Pu, (^240)Pu, (^241)Pu, antineutrino and electron spectra calculated. Ď for νĚ
induced reactions analyzed.
Probing minimal supergravity in the type-I seesaw mechanism with lepton flavour violation at the CERN LHC
The most general supersymmetric seesaw mechanism has too many parameters to
be predictive and thus can not be excluded by any measurements of lepton
flavour violating (LFV) processes. We focus on the simplest version of the
type-I seesaw mechanism assuming minimal supergravity boundary conditions. We
compute branching ratios for the LFV scalar tau decays, , as well as loop-induced LFV decays at low energy, such as
and , exploring their sensitivity to the
unknown seesaw parameters. We find some simple, extreme scenarios for the
unknown right-handed parameters, where ratios of LFV branching ratios correlate
with neutrino oscillation parameters. If the overall mass scale of the left
neutrinos and the value of the reactor angle were known, the study of LFV
allows, in principle, to extract information about the so far unknown
right-handed neutrino parameters.Comment: 29 pages, 27 figures; added explanatory comments, corrected typos,
final version for publicatio
Pair Production of Topological anti de Sitter Black Holes
The pair creation of black holes with event horizons of non-trivial topology
is described. The spacetimes are all limiting cases of the cosmological
metric. They are generalizations of the dimensional black hole and have
asymptotically anti de Sitter behaviour. Domain walls instantons can mediate
their pair creation for a wide range of mass and charge.Comment: 4 pages, uses late
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