296 research outputs found
Production in Peripheral Heavy-Ion Collisions
We estimate the impact parameter dependence of the production cross section
for and mesons in peripheral heavy-ion collisions collisions.
Total and elastic cross sections are calculated in an equivalent
photon approximation.Comment: 9 pages, uuencoded postscrip
Illuminating spindle convex bodies and minimizing the volume of spherical sets of constant width
A subset of the d-dimensional Euclidean space having nonempty interior is
called a spindle convex body if it is the intersection of (finitely or
infinitely many) congruent d-dimensional closed balls. The spindle convex body
is called a "fat" one, if it contains the centers of its generating balls. The
core part of this paper is an extension of Schramm's theorem and its proof on
illuminating convex bodies of constant width to the family of "fat" spindle
convex bodies.Comment: 17 page
Photon-Photon and Pomeron-Pomeron Processes in Peripheral Heavy Ion Collisions
We estimate the cross sections for the production of resonances, pion pairs
and a central cluster of hadrons in peripheral heavy-ion collisions through
two-photon and double-pomeron exchange, at energies that will be available at
RHIC and LHC. The effect of the impact parameter in the diffractive reactions
is introduced, and imposing the condition for realistic peripheral collisions
we verify that in the case of very heavy ions the pomeron-pomeron contribution
is indeed smaller than the electromagnetic one. However, they give a
non-negligible background in the collision of light ions. This diffractive
background will be more important at RHIC than at LHC.Comment: 22 pages, 1 Postscript figures, 4 tables, to appear in Phys. Rev.
The near-critical planar FK-Ising model
We study the near-critical FK-Ising model. First, a determination of the
correlation length defined via crossing probabilities is provided. Second, a
phenomenon about the near-critical behavior of FK-Ising is highlighted, which
is completely missing from the case of standard percolation: in any monotone
coupling of FK configurations (e.g., in the one introduced in
[Gri95]), as one raises near , the new edges arrive in a
self-organized way, so that the correlation length is not governed anymore by
the number of pivotal edges at criticality.Comment: 34 pages, 8 figures. This is a streamlined version; the previous one
contains more explanations and additional material on exceptional times in FK
models with general . Furthermore, the statement and proof of Theorem 1.2
have slightly change
Hopf algebras and Markov chains: Two examples and a theory
The operation of squaring (coproduct followed by product) in a combinatorial
Hopf algebra is shown to induce a Markov chain in natural bases. Chains
constructed in this way include widely studied methods of card shuffling, a
natural "rock-breaking" process, and Markov chains on simplicial complexes.
Many of these chains can be explictly diagonalized using the primitive elements
of the algebra and the combinatorics of the free Lie algebra. For card
shuffling, this gives an explicit description of the eigenvectors. For
rock-breaking, an explicit description of the quasi-stationary distribution and
sharp rates to absorption follow.Comment: 51 pages, 17 figures. (Typographical errors corrected. Further fixes
will only appear on the version on Amy Pang's website, the arXiv version will
not be updated.
Updated Nucleosynthesis Constraints on Unstable Relic Particles
We revisit the upper limits on the abundance of unstable massive relic
particles provided by the success of Big-Bang Nucleosynthesis calculations. We
use the cosmic microwave background data to constrain the baryon-to-photon
ratio, and incorporate an extensively updated compilation of cross sections
into a new calculation of the network of reactions induced by electromagnetic
showers that create and destroy the light elements deuterium, he3, he4, li6 and
li7. We derive analytic approximations that complement and check the full
numerical calculations. Considerations of the abundances of he4 and li6 exclude
exceptional regions of parameter space that would otherwise have been permitted
by deuterium alone. We illustrate our results by applying them to massive
gravitinos. If they weigh ~100 GeV, their primordial abundance should have been
below about 10^{-13} of the total entropy. This would imply an upper limit on
the reheating temperature of a few times 10^7 GeV, which could be a potential
difficulty for some models of inflation. We discuss possible ways of evading
this problem.Comment: 40 pages LaTeX, 18 eps figure
Ultrapotent antibodies against diverse and highly transmissible SARS-CoV-2 variants
IC80 1.5 to 34.5 nanograms per milliliter). We define the structural and functional determinants of binding for all four VOC-targeting antibodies and show that combinations of two antibodies decrease the in vitro generation of escape mutants, suggesting their potential in mitigating resistance development.The emergence of highly transmissible SARS-CoV-2 variants of concern (VOCs) that are resistant to therapeutic antibodies highlights the need for continuing discovery of broadly reactive antibodies. We identified four receptor binding domain-targeting antibodies from three early-outbreak convalescent donors with potent neutralizing activity against 23 variants, including the B.1.1.7, B.1.351, P.1, B.1.429, B.1.526, and B.1.617 VOCs. Two antibodies are ultrapotent, with subnanomolar neutralization titers [half-maximal inhibitory concentration (IC50) 0.3 to 11.1 nanograms per millilite
Efeito da carga animal na produção de leite de vacas de corte primíparas e no desenvolvimento de seus bezerros
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