6,002 research outputs found
Calculating the hadronic vacuum polarization and leading hadronic contribution to the muon anomalous magnetic moment with improved staggered quarks
We present a lattice calculation of the hadronic vacuum polarization and the
lowest-order hadronic contribution to the muon anomalous magnetic moment, a_\mu
= (g-2)/2, using 2+1 flavors of improved staggered fermions. A precise fit to
the low-q^2 region of the vacuum polarization is necessary to accurately
extract the muon g-2. To obtain this fit, we use staggered chiral perturbation
theory, including the vector particles as resonances, and compare these to
polynomial fits to the lattice data. We discuss the fit results and associated
systematic uncertainties, paying particular attention to the relative
contributions of the pions and vector mesons. Using a single lattice spacing
ensemble (a=0.086 fm), light quark masses as small as roughly one-tenth the
strange quark mass, and volumes as large as (3.4 fm)^3, we find a_\mu^{HLO} =
(713 \pm 15) \times 10^{-10} and (748 \pm 21) \times 10^{-10} where the error
is statistical only and the two values correspond to linear and quadratic
extrapolations in the light quark mass, respectively. Considering systematic
uncertainties not eliminated in this study, we view this as agreement with the
current best calculations using the experimental cross section for e^+e^-
annihilation to hadrons, 692.4 (5.9) (2.4)\times 10^{-10}, and including the
experimental decay rate of the tau lepton to hadrons, 711.0 (5.0)
(0.8)(2.8)\times 10^{-10}. We discuss several ways to improve the current
lattice calculation.Comment: 44 pages, 4 tables, 17 figures, more discussion on matching the chpt
calculation to lattice calculation, typos corrected, refs added, version to
appear in PR
On the theoretical uncertainties in the muon anomalous magnetic moment
I present a fairly detailed discussion of various contributions to the
anomalous magnetic moment of the muon a_mu. I try to give an unbiased
evaluation of the validity of the SM prediction for this quantity and to point
out some delicate issues involved in its calculation. I conclude that the
theory uncertainties in the SM prediction for the muon anomalous magnetic
moment are underestimated and a great deal of work will be required to reduce
these uncertainties to the level required by experiment.Comment: 12 pages, revte
Potentialities of proteinoids for nutritional investigation
Simultaneous synthesis of amino acids and proteinoid production for nutritional investigatio
Condensation of Hard Spheres Under Gravity
Starting from Enskog equation of hard spheres of mass m and diameter D under
the gravity g, we first derive the exact equation of motion for the equilibrium
density profile at a temperature T and examine its solutions via the gradient
expansion. The solutions exist only when \beta\mu \le \mu_o \approx 21.756 in 2
dimensions and \mu_o\approx 15.299 in 3 dimensions, where \mu is the
dimensionless initial layer thickness and \beta=mgD/T. When this inequality
breaks down, a fraction of particles condense from the bottom up to the Fermi
surface.Comment: 9 pages, one figur
Condensation of Hard Spheres Under Gravity: Exact Results in One Dimension
We present exact results for the density profile of the one dimensional array
of N hard spheres of diameter D and mass m under gravity g. For a strictly one
dimensional system, the liquid-solid transition occurs at zero temperature,
because the close-pakced density, , is one. However, if we relax this
condition slightly such that , we find a series of critical
temperatures T_c^i=mgD(N+1-i)/\mu_o with \mu_o=const, at which the i-th
particle undergoes the liquid-solid transition. The functional form of the
onset temperature, T_c^1=mgDN/\mu_o, is consistent with the previous result
[Physica A 271, 192 (1999)] obtained by the Enskog equation. We also show that
the increase in the center of mass is linear in T before the transition, but it
becomes quadratic in T after the transition because of the formation of solid
near the bottom
Hydrodynamic Description of Granular Convection
We present a hydrodynamic model that captures the essence of granular
dynamics in a vibrating bed. We carry out the linear stability analysis and
uncover the instability mechanism that leads to the appearance of the
convective rolls via a supercritical bifurcation of a bouncing solution. We
also explicitly determine the onset of convection as a function of control
parameters and confirm our picture by numerical simulations of the continuum
equations.Comment: 14 pages, RevTex 11pages + 3 pages figures (Type csh
Thermodynamic Theory of Weakly Excited Granular Materials
We present a thermodynamic theory of weakly excited two-dimensional granular
systems from the view point of elementary excitations of spinless Fermion
systems. We introduce a global temperature T that is associated with the
acceleration amplitude \Gamma in a vibrating bed. We show that the
configurational statistics of weakly excited granular materials in a vibrating
bed obey the Fermi statistics.Comment: 12 pages, 1 figure, To Appear in Phys. Rev. Lett. April, 199
Fracture driven by a Thermal Gradient
Motivated by recent experiments by Yuse and Sano (Nature, 362, 329 (1993)),
we propose a discrete model of linear springs for studying fracture in thin and
elastically isotropic brittle films. The method enables us to draw a map of the
stresses in the material. Cracks generated by the model, imposing a moving
thermal gradient in the material, can branch or wiggle depending on the driving
parameters. The results may be used to compare with other recent theoretical
work, or to design future experiments.Comment: RevTeX file (9 pages) and 5 postscript figure
Fermionic Contributions to the Free Energy of Noncommutative Quantum Electrodynamics at High Temperature
We consider the fermionic contributions to the free energy of noncommutative
QED at finite temperature . This analysis extends the main results of our
previous investigation where we have considered the pure bosonic sector of the
theory. For large values of ( is the magnitude of the
noncommutative parameters) the fermionic contributions decrease the value of
the critical temperature, above which there occurs a thermodynamic instability.Comment: 6 pages, 3 figures. To be published in Physics Letters
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