1,002 research outputs found
Holographic model for dilepton production in p-p collisions
We propose a holographic model for dilepton production in proton-proton
collisions based on the exchange of vector mesons. The holographic hard wall
model is used to describe the dynamics and interactions of vector mesons and
baryons. We estimate the parameters lambda, mu, nu that characterize the
angular distribution of the produced dileptons in a region of q_T^2 << Q^2,
where perturbative QCD presents an effective strong coupling due to large
logarithm corrections.Comment: Revision: V4 In this version we modified the dimension of the
fermionic operator to match the canonical dimension of a baryonic operator.
This modification affected slightly our results with respect to v3. 25 pages,
3 Latex figures + 6 eps figures, 5 tables. To appear in Nucl. Phys.
Beyond single-photon localization at the edge of a Photonic Band Gap
We study spontaneous emission in an atomic ladder system, with both
transitions coupled near-resonantly to the edge of a photonic band gap
continuum. The problem is solved through a recently developed technique and
leads to the formation of a ``two-photon+atom'' bound state with fractional
population trapping in both upper states. In the long-time limit, the atom can
be found excited in a superposition of the upper states and a ``direct''
two-photon process coexists with the stepwise one. The sensitivity of the
effect to the particular form of the density of states is also explored.Comment: to appear in Physical Review
Induced Parity-Breaking Term at Finite Chemical Potential and Temparature
We exactly calculated the parity-odd term of the effective action induced by
the fermions in 2+1 dimensions at finite chemical potential and finite
temperature. It shows that gauge invariance is still respected. A more gerneral
class of background configurations is considered. The knowledge of the reduced
1+1 determinant is required in order to draw exact conclusions about the gauge
invariance of the parity-odd term in this latter case.Comment: 8 pages, LATEX, no figure
Solving 2D-pattern matching with networks of picture processors
We propose a solution based on networks of picture processors to the problem of picture pattern matching. The network solving the problem can be informally described as follows: it consists of two subnetworks, one of them extracts simultaneously all subpictures of the same size from the input picture and sends them to the second subnetwork. The second subnetwork checks whether any of the received pictures is identical to the pattern. We present an efficient solution based on networks with evolutionary processors only, for patterns with at most three rows or columns. Afterwards, we present a solution based on networks containing both evolutionary and hiding processors running in O(n+m+kl+k) computational (processing and communication) steps, where the input picture and the pattern are of size (n,m) and (k,l), respectively
A microsatellite marker for yellow rust resistance in wheat
Bulk segregant analysis (BSA) was used to identify molecular markers associated with yellow rust disease resistance in wheat (Triticum aestivum L.). DNAs isolated from the selected yellow rust tolerant and susceptible F-2 individuals derived from a cross between yellow rust resistant and susceptible wheat genotypes were used to established a "tolerant" and a "susceptible" DNA pool. The BSA was then performed on these DNA pools using 230 markers that were previously mapped onto the individual wheat chromosomes. One of the SSR markers (Xgwm382) located on chromosome group 2 (A, B, D genomes) was present in the resistant parent and the resistant bulk but not in the susceptible parent and the susceptible bulk, suggesting that this marker is linked to a yellow rust resistance gene. The presence of Xgwm382 was also tested in 108 additional wheat genotypes differing in yellow rust resistance. This analysis showed that 81% of the wheat genotypes known to be yellow rust resistant had the Xgwm382 marker, further suggesting that the presence of this marker correlates with yellow rust resistance in diverse wheat germplasm. Therefore, Xgwm382 could be useful for marker assisted selection of yellow rust resistances genotypes in wheat breeding programs
Benzene with Alkyl Chains Is a Universal Scaffold for Multivalent Virucidal Antivirals.
Most viruses start their invasion by binding to glycoproteins' moieties on the cell surface (heparan sulfate proteoglycans [HSPG] or sialic acid [SA]). Antivirals mimicking these moieties multivalently are known as broad-spectrum multivalent entry inhibitors (MEI). Due to their reversible mechanism, efficacy is lost when concentrations fall below an inhibitory threshold. To overcome this limitation, we modify MEIs with hydrophobic arms rendering the inhibitory mechanism irreversible, i.e., preventing the efficacy loss upon dilution. However, all our HSPG-mimicking MEIs only showed reversible inhibition against HSPG-binding SARS-CoV-2. Here, we present a systematic investigation of a series of small molecules, all containing a core and multiple hydrophobic arms terminated with HSPG-mimicking moieties. We identify the ones that have irreversible inhibition against all viruses including SARS-CoV-2 and discuss their design principles. We show efficacy in vivo against SARS-CoV-2 in a Syrian hamster model through both intranasal instillation and aerosol inhalation in a therapeutic setting (12 h postinfection). We also show the utility of the presented design rules in producing SA-mimicking MEIs with irreversible inhibition against SA-binding influenza viruses
Geometric Entanglement of Symmetric States and the Majorana Representation
Permutation-symmetric quantum states appear in a variety of physical
situations, and they have been proposed for quantum information tasks. This
article builds upon the results of [New J. Phys. 12, 073025 (2010)], where the
maximally entangled symmetric states of up to twelve qubits were explored, and
their amount of geometric entanglement determined by numeric and analytic
means. For this the Majorana representation, a generalization of the Bloch
sphere representation, can be employed to represent symmetric n qubit states by
n points on the surface of a unit sphere. Symmetries of this point distribution
simplify the determination of the entanglement, and enable the study of quantum
states in novel ways. Here it is shown that the duality relationship of
Platonic solids has a counterpart in the Majorana representation, and that in
general maximally entangled symmetric states neither correspond to anticoherent
spin states nor to spherical designs. The usability of symmetric states as
resources for measurement-based quantum computing is also discussed.Comment: 10 pages, 8 figures; submitted to Lecture Notes in Computer Science
(LNCS
The theta^+ baryon in soliton models: large Nc QCD and the validity of rigid-rotor quantization
A light collective theta+ baryon state (with strangeness +1) was predicted
via rigid-rotor collective quantization of SU(3) chiral soliton models. This
paper explores the validity of this treatment. A number of rather general
analyses suggest that predictions of exotic baryon properties based on this
approximation do not follow from large Nc QCD. These include an analysis of the
baryon's width, a comparison of the predictions with general large Nc
consistency conditions of the Gervais-Sakita-Dashen-Manohar type; an
application of the technique to QCD in the limit where the quarks are heavy; a
comparison of this method with the vibration approach of Callan and Klebanov;
and the 1/Nc scaling of the excitation energy. It is suggested that the origin
of the problem lies in an implicit assumption in the that the collective motion
is orthogonal to vibrational motion. While true for non-exotic motion, the
Wess-Zumino term induces mixing at leading order between collective and
vibrational motion with exotic quantum numbers. This suggests that successful
phenomenological predictions of theta+ properties based on rigid-rotor
quantization were accidental.Comment: 19 pages; A shorter more readable versio
Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets
The spins of ten stellar black holes have been measured using the
continuum-fitting method. These black holes are located in two distinct classes
of X-ray binary systems, one that is persistently X-ray bright and another that
is transient. Both the persistent and transient black holes remain for long
periods in a state where their spectra are dominated by a thermal accretion
disk component. The spin of a black hole of known mass and distance can be
measured by fitting this thermal continuum spectrum to the thin-disk model of
Novikov and Thorne; the key fit parameter is the radius of the inner edge of
the black hole's accretion disk. Strong observational and theoretical evidence
links the inner-disk radius to the radius of the innermost stable circular
orbit, which is trivially related to the dimensionless spin parameter a_* of
the black hole (|a_*| < 1). The ten spins that have so far been measured by
this continuum-fitting method range widely from a_* \approx 0 to a_* > 0.95.
The robustness of the method is demonstrated by the dozens or hundreds of
independent and consistent measurements of spin that have been obtained for
several black holes, and through careful consideration of many sources of
systematic error. Among the results discussed is a dichotomy between the
transient and persistent black holes; the latter have higher spins and larger
masses. Also discussed is recently discovered evidence in the transient sources
for a correlation between the power of ballistic jets and black hole spin.Comment: 30 pages. Accepted for publication in Space Science Reviews. Also to
appear in hard cover in the Space Sciences Series of ISSI "The Physics of
Accretion onto Black Holes" (Springer Publisher). Changes to Sections 5.2,
6.1 and 7.4. Section 7.4 responds to Russell et al. 2013 (MNRAS, 431, 405)
who find no evidence for a correlation between the power of ballistic jets
and black hole spi
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