21,410 research outputs found
Ultrapure glass optical waveguide: Development in microgravity by the sol gel process
The sol-gel process for the preparation of homogeneous gels in three binary oxide systems was investigated. The glass forming ability of certain compositions in the selected oxide systems (SiO-GeO2, GeO2-PbO, and SiO2-TiO2) were studied based on their potential importance in the design of optical waveguide at longer wavelengths
Precise Variational Calculation For The Doubly Excited State (2p^2)^3P^e of Helium
Highly precise variational calculations of non-relativistic energies of the
(2p^2)^3P^e state of Helium atom are presented.We get an upper bound energy
E=-0.71050015565678 a.u.,the lowest yet obtained.Comment: 5 pages, 1 tabl
A model independent analysis of gluonic pole matrix elements and universality of TMD fragmentation functions
Gluonic pole matrix elements explain the appearance of single spin
asymmetries (SSA) in high-energy scattering processes. They involve a
combination of operators which are odd under time reversal (T-odd). Such matrix
elements appear in principle both for parton distribution functions and parton
fragmentation functions. We show that for parton fragmentation functions these
gluonic pole matrix elements vanish as a consequence of the analytic structure
of scattering amplitudes in Quantum Chromodynamics. This result is important in
the study of the universality of transverse momentum dependent (TMD)
fragmentation functions.Comment: 5 pages, 5 figures, version to appear in Phys. Rev.
Next-to-leading order QCD corrections to single-inclusive hadron production in transversely polarized p-p and pbar-p collisions
We present a calculation of the next-to-leading order QCD corrections to the
partonic cross sections contributing to single-inclusive high-p_T hadron
production in collisions of transversely polarized hadrons. We use a recently
developed projection technique for treating the phase space integrals in the
presence of the cos(2Phi) azimuthal-angular dependence associated with
transverse polarization. Our phenomenological results show that the double-spin
asymmetry A_TT^pi for neutral-pion production is expected to be very small for
polarized pp scattering at RHIC and could be much larger for the proposed
experiments with an asymmetric pbar-p collider at the GSIComment: 7 pages, 5 figure
Evaporative segregation in 80 percent Ni-20 percent Cr and 60 percent Fe-40 percent Ni alloys
The phenomenon of evaporative segregation in binary alloys has been investigated through a study of some experimental evaporation data relating to the Ni-Cr and Ni-Fr systems. In normal evaporation it is assumed that (1) the evaporating alloy is always homogeneous, (2) the vapor is instantly removed, and (3) the alloy follows Raoult's law. The solutions of the evaporation equations for the two most important cases are presented and experimental data are analyzed with these equations. The difference between observed and calculated values of evaporation constants lies within one order of magnitude. This is surprising because of the major assumptions stated above. Experimental results have shown that the evaporation time and final solute concentration are logarithmically related, further supporting our evaporation equations. It is further shown that neglecting the nonlogarithmic term in these evaporation equations may introduce considerable errors in the analysis
Kinematical Analogy for Marginal Dyon Decay
We describe a kinematical analogy for the marginal decay of 1/4-BPS dyons in
4-dimensional N=4 string compactifications. In this analogy, the electric and
magnetic charges play the role of spatial momenta, the BPS mass plays the role
of energy, and 1/2-BPS dyons correspond to massless particles. Using SO(12,1)
"Lorentz" invariance and standard kinematical formulae in particle physics, we
provide simple derivations of the curves of marginal stability. We also show
how these curves map into the momentum ellipsoid, and propose some applications
of this analogy.Comment: 10 pages, minor revision
Universality of Load Balancing Schemes on Diffusion Scale
We consider a system of parallel queues with identical exponential
service rates and a single dispatcher where tasks arrive as a Poisson process.
When a task arrives, the dispatcher always assigns it to an idle server, if
there is any, and to a server with the shortest queue among randomly
selected servers otherwise . This load balancing scheme
subsumes the so-called Join-the-Idle Queue (JIQ) policy and the
celebrated Join-the-Shortest Queue (JSQ) policy as two crucial
special cases. We develop a stochastic coupling construction to obtain the
diffusion limit of the queue process in the Halfin-Whitt heavy-traffic regime,
and establish that it does not depend on the value of , implying that
assigning tasks to idle servers is sufficient for diffusion level optimality
Theory of the magnetoeletric effect in a lightly doped high-Tc cuprate
In a recent study Viskadourakis et al. discovered that extremely underdoped
La_2CuO_(4+x) is a relaxor ferroelectric and a magnetoelectric material at low
temperatures. It is further observed that the magnetoelectric response is
anisotropic for different directions of electric polarization and applied
magnetic field. By constructing an appropriate Landau theory, we show that a
bi-quadratic magnetoelectric coupling can explain the experimentally observed
polarization dependence on magnetic field. This coupling leads to several novel
low-temperature effects including a feedback enhancement of the magnetization
below the ferroelectric transition, and a predicted magnetocapacitive effect.Comment: 5 pages, 4 figure
Planck priors for dark energy surveys
Although cosmic microwave background (CMB) anisotropy data alone cannot
constrain simultaneously the spatial curvature and the equation of state of
dark energy, CMB data provide a valuable addition to other experimental
results. However computing a full CMB power spectrum with a Boltzmann code is
quite slow; for instance if we want to work with many dark energy and/or
modified gravity models, or would like to optimize experiments where many
different configurations need to be tested, it is possible to adopt a quicker
and more efficient approach.
In this paper we consider the compression of the projected Planck CMB data
into four parameters, R (scaled distance to last scattering surface), l_a
(angular scale of sound horizon at last scattering), Omega_b h^2 (baryon
density fraction) and n_s (powerlaw index of primordial matter power spectrum),
all of which can be computed quickly. We show that, although this compression
loses information compared to the full likelihood, such information loss
becomes negligible when more data is added. We also demonstrate that the method
can be used for scalar field dark energy independently of the parametrisation
of the equation of state, and discuss how this method should be used for other
kinds of dark energy models.Comment: 8 pages, 3 figures, 4 table
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