1,445 research outputs found
Pion wave functions from holographic QCD and the role of infrared renormalons in photon-photon collisions
In this article, we calculate the contribution of the higher-twist Feynman
diagrams to the large- inclusive single pion production cross section in
photon-photon collisions in case of the running coupling and frozen coupling
approaches within holographic QCD. We compare the resummed higher-twist cross
sections with the ones obtained in the framework of the frozen coupling
approach and leading-twist cross section. Also, we show that in the context of
frozen coupling approach a higher-twist contribution to the photon-photon
collisions cross section is normalized in terms of the pion electromagnetic
form factor.Comment: 21 pages, 15 figures. arXiv admin note: text overlap with
arXiv:0709.2072 by other author
Looking Back From the Future: Perspective Taking in Virtual Reality Increases Future Self-Continuity
In the current study, we tested a novel perspective-taking exercise aimed at increasing the connection participants felt toward their future self, i.e., future self-continuity. Participants role-played as their successful future self and answered questions about what it feels like to become their future and the path to get there. The exercise was also conducted in a virtual reality environment and in vivo to investigate the possible added value of the virtual environment with respect to improved focus, perspective-taking, and effectiveness for participants with less imagination. Results show that the perspective taking exercise in virtual reality substantially increased all four domains of future self-continuity, i.e., connectedness, similarity, vividness, and liking, while the in vivo equivalent increased only liking and vividness. Although connectedness and similarity were directionally, but not significantly different between the virtual and in vivo environments, neither the focus, perspective taking, or individual differences in imagination could explain this difference—which suggests a small, but non-significant, placebo effect of the virtual reality environment. However, lower baseline vividness in the in vivo group may explain this difference and suggests preliminary evidence for the dependency of connectedness and similarity domains upon baseline vividness. These findings show that the perspective taking exercise in a VR environment can reliably increase the future self-continuity domains
Determination of III-V/Si absolute interface energies: impact on wetting properties
Here, we quantitatively determine the impact of III-V/Si interface atomic
configuration on the wetting properties of the system. Based on a description
at the atomic scale using density functional theory, we first show that it is
possible to determine the absolute interface energies in heterogeneous
materials systems. A large variety of absolute GaP surface energies and GaP/Si
interface energies are then computed, confirming the large stability of charge
compensated III-V/Si interfaces with an energy as low as 23 meV/\r{A}.
While stable compensated III-V/Si interfaces are expected to promote complete
wetting conditions, it is found that this can be easily counterbalanced by the
substrate initial passivation, which favors partial wetting conditions.Comment: 17 pages, 14 figure
On QCD analysis of stucture function in alternative approach
The alternative approach to QCD analysis of the photon structure function
is presented. It differs from the conventional one by the
presence of the terms which in conventional approach appear in higher orders.
We show that this difference concerns also the photonic parton distribution
functions. In the alternative approach, the complete LO analysis of
can be performed as all required quantities are known. At the
NLO, however, one of the coefficient function is so far not available and thus
only the photonic parton distribution function can be computed and compared to
those of standard approach. We discuss the numerical difference of these
approaches at the LO and the NLO approximation and show that in case of
this difference is non-negligible and may play an important role
in the analysis on photon data of the future experiments.Comment: 25 page
La calorimetrÃa diferencial de barrido y su aplicación a la Ciencia de Materiales
Se pone de manifiesto la idoneidad de la técnica de calorimetrÃa diferencial de barrido para la caracterización de materiales. Se presentan ejemplos especÃficos de aplicación de dicha técnica en el estudio de los fenómenos ligados a la transición vitrea y cinética de cristalización de vidrios calcogenuros y metálicos asà como en el estudio de la reordenación de fases desordenadas metastables
Cosmic Rays and Large Extra Dimensions
We have proposed that the cosmic ray spectrum "knee", the steepening of the
cosmic ray spectrum at energy E \gsim 10^{15.5} eV, is due to "new physics",
namely new interactions at TeV cm energies which produce particles undetected
by the experimental apparatus. In this letter we examine specifically the
possibility that this interaction is low scale gravity. We consider that the
graviton propagates, besides the usual four dimensions, into an additional
, compactified, large dimensions and we estimate the graviton
production in collisions in the high energy approximation where graviton
emission is factorized. We find that the cross section for graviton production
rises as fast as , where is the fundamental
scale of gravity in dimensions, and that the distribution of
radiating a fraction of the initial particle's energy into gravitational
energy (which goes undetected) behaves as . The missing
energy leads to an underestimate of the true energy and generates a break in
the {\sl inferred} cosmic ray spectrum (the "kne"). By fitting the cosmic ray
spectrum data we deduce that the favorite values for the parameters of the
theory are TeV and .Comment: 8 pages, 1 figur
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