610 research outputs found
Quantum Gambling Using Two Nonorthogonal States
We give a (remote) quantum gambling scheme that makes use of the fact that
quantum nonorthogonal states cannot be distinguished with certainty. In the
proposed scheme, two participants Alice and Bob can be regarded as playing a
game of making guesses on identities of quantum states that are in one of two
given nonorthogonal states: if Bob makes a correct (an incorrect) guess on the
identity of a quantum state that Alice has sent, he wins (loses). It is shown
that the proposed scheme is secure against the nonentanglement attack. It can
also be shown heuristically that the scheme is secure in the case of the
entanglement attack.Comment: no essential correction, 4 pages, RevTe
Probing Cosmic Strings with Satellite CMB measurements
We study the problem of searching for cosmic string signal patterns in the
present high resolution and high sensitivity observations of the Cosmic
Microwave Background (CMB). This article discusses a technique capable of
recognizing Kaiser-Stebbins effect signatures in total intensity anisotropy
maps, and shows that the biggest factor that produces confusion is represented
by the acoustic oscillation features of the scale comparable to the size of
horizon at recombination. Simulations show that the distribution of null
signals for pure Gaussian maps converges to a distribution, with
detectability threshold corresponding to a string induced step signal with an
amplitude of about 100 \muK which corresponds to a limit of roughly . We study the statistics of spurious detections caused by
extra-Galactic and Galactic foregrounds. For diffuse Galactic foregrounds,
which represents the dominant source of contamination, we derive sky masks
outlining the available region of the sky where the Galactic confusion is
sub-dominant, specializing our analysis to the case represented by the
frequency coverage and nominal sensitivity and resolution of the Planck
experiment.Comment: 14 pages, 3 figures, to be published in JCA
Lipidomic profile as a non-invasive tool to predict endometrial receptivity in freeze-all cycles
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Creating the cultures of the future: cultural strategy, policy and institutions in Gramsci. Part three: Is there a theory of cultural policy in Gramsci’s prison notebooks?
In this article, I argue that Gramsci’s prison notes on questions of cultural strategy, policy and institutions, which have so far been largely overlooked by scholars, provide further analytical insights to those offered by his more general concepts. Together they enrich the theoretical underpinnings for critical frameworks of analysis as well as for radical practices of cultural strategy, cultural policy-making and cultural organisation. On the basis of a detailed analysis of these notes, I then answer the question of whether they amount to a theory of cultural policy
The 21 cm Signature of Cosmic String Wakes
We discuss the signature of a cosmic string wake in 21cm redshift surveys.
Since 21cm surveys probe higher redshifts than optical large-scale structure
surveys, the signatures of cosmic strings are more manifest in 21cm maps than
they are in optical galaxy surveys. We find that, provided the tension of the
cosmic string exceeds a critical value (which depends on both the redshift when
the string wake is created and the redshift of observation), a cosmic string
wake will generate an emission signal with a brightness temperature which
approaches a limiting value which at a redshift of is close to 400
mK in the limit of large string tension. The signal will have a specific
signature in position space: the excess 21cm radiation will be confined to a
wedge-shaped region whose tip corresponds to the position of the string, whose
planar dimensions are set by the planar dimensions of the string wake, and
whose thickness (in redshift direction) depends on the string tension. For
wakes created at , then at a redshift of the
critical value of the string tension is , and
it decreases linearly with redshift (for wakes created at the time of equal
matter and radiation, the critical value is a factor of two lower at the same
redshift). For smaller tensions, cosmic strings lead to an observable
absorption signal with the same wedge geometry.Comment: 11 pages, 4 figures; a couple of comments added in the discussion
sectio
Edge Detection, Cosmic Strings and the South Pole Telescope
We develop a method of constraining the cosmic string tension which
uses the Canny edge detection algorithm as a means of searching CMB temperature
maps for the signature of the Kaiser-Stebbins effect. We test the potential of
this method using high resolution, simulated CMB temperature maps. By modeling
the future output from the South Pole Telescope project (including anticipated
instrumental noise), we find that cosmic strings with
could be detected.Comment: 27 pages, 5 figures, reference and minor notes added, discussion of
noise expanded, explanation of equation (4) expande
Experimental study of negative photoconductivity in n-PbTe(Ga) epitaxial films
We report on low-temperature photoconductivity (PC) in n-PbTe(Ga) epitaxial
films prepared by the hot-wall technique on -BaF_2 substrates. Variation
of the substrate temperature allowed us to change the resistivity of the films
from 10^8 down to 10_{-2} Ohm x cm at 4.2 K. The resistivity reduction is
associated with a slight excess of Ga concentration, disturbing the Fermi level
pinning within the energy gap of n-PbTe(Ga). PC has been measured under
continuous and pulse illumination in the temperature range 4.2-300 K. For films
of low resistivity, the photoresponse is composed of negative and positive
parts. Recombination processes for both effects are characterized by
nonexponential kinetics depending on the illumination pulse duration and
intensity. Analysis of the PC transient proves that the negative
photoconductivity cannot be explained in terms of nonequilibrium charge
carriers spatial separation of due to band modulation. Experimental results are
interpreted assuming the mixed valence of Ga in lead telluride and the
formation of centers with a negative correlation energy. Specifics of the PC
process is determined by the energy levels attributed to donor Ga III, acceptor
Ga I, and neutral Ga II states with respect to the crystal surrounding. The
energy level corresponding to the metastable state Ga II is supposed to occur
above the conduction band bottom, providing fast recombination rates for the
negative PC. The superposition of negative and positive PC is considered to be
dependent on the ratio of the densities of states corresponding to the donor
and acceptor impurity centers.Comment: 7 pages, 4 figure
Gravitational Lensing by Black Holes
We review the theoretical aspects of gravitational lensing by black holes,
and discuss the perspectives for realistic observations. We will first treat
lensing by spherically symmetric black holes, in which the formation of
infinite sequences of higher order images emerges in the clearest way. We will
then consider the effects of the spin of the black hole, with the formation of
giant higher order caustics and multiple images. Finally, we will consider the
perspectives for observations of black hole lensing, from the detection of
secondary images of stellar sources and spots on the accretion disk to the
interpretation of iron K-lines and direct imaging of the shadow of the black
hole.Comment: Invited article for the GRG special issue on lensing (P. Jetzer, Y.
Mellier and V. Perlick Eds.). 31 pages, 12 figure
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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