14,605 research outputs found
Interplay of Hard and Soft Processes at JLab Energies
Even at moderate energy machines, there is a regime where hard pion
electroproduction proceeds by a perturbatively calculable process. The process,
we claim, is not the leading twist fragmentation one but rather a higher twist
process that produces kinematically isolated pions. Semiexclusive data may
teach us more about parton distribution functions of the target and the pion
distribution amplitude. In addition, there is a connection to generalized
parton distribution calculations of exclusive processes in that the
perturbative kernel is the same.Comment: 8 pages, 9 figures, Written version of invited talk by CEC at the
Second International Symposium on the Gerasimov-Drell-Hearn sum rule and the
spin structure of the nucleon (GDH2002), Genoa, Italy, 3--6 July 2002, and of
talk by CEC under the title ``Hard Pion Electroproduction at Medium
Energies'' at the XVI International Conference on Particles and Nuclei
(PANIC02), Osaka, Japan, 30 September--4 October 2002 [WM-02-111;
JLAB-THY-02-62
Squeezing in the weakly interacting uniform Bose condensate
We investigate the presence of squeezing in the weakly repulsive uniform Bose
gas, in both the condensate mode and in the nonzero opposite-momenta mode
pairs, using two different variational formulations. We explore the U(1)
symmetry breaking and Goldstone's theorem in the context of a squeezed coherent
variational wavefunction, and present the associated Ward identity. We show
that squeezing of the condensate mode is absent at the mean field
Hartree-Fock-Bogoliubov level and emerges as a result of fluctuations about
mean field as a finite volume effect, which vanishes in the thermodynamic
limit. On the other hand, the squeezing of the excitations about the condensate
survives the thermodynamic limit and is interpreted in terms of density-phase
variables using a number-conserving formulation of the interacting Bose gas.Comment: 8 pages, 3 figures. Version 2 (Sept'06): expanded discussion
From surface to volume plasmons in hyperbolic metamaterials: General existence conditions for bulk high-k waves in metal-dielectric and graphene-dielectric multilayers
We theoretically investigate general existence conditions for broadband bulk
large-wavevector (high-k) propagating waves (such as volume plasmon polaritons
in hyperbolic metamaterials) in subwavelength periodic multilayer structures.
Describing the elementary excitation in the unit cell of the structure by a
generalized resonance pole of a reflection coefficient, and using Bloch's
theorem, we derive analytical expressions for the band of large-wavevector
propagating solutions. We apply our formalism to determine the high-k band
existence in two important cases: the well-known metal-dielectric, and recently
introduced graphene-dielectric stacks. We confirm that short-range surface
plasmons in thin metal layers can give rise to hyperbolic metamaterial
properties, and demonstrate that long-range surface plasmons cannot. We also
show that graphene-dielectric multilayers tend to support high-k waves and
explore the range of parameters for which this is possible, confirming the
prospects of using graphene for materials with hyperbolic dispersion. The
approach is applicable to a large variety of structures, such as continuous or
structured microwave, terahertz (THz) and optical metamaterials.Comment: 9 pages, 5 figure
Extended Tensor Products and Generalization of the Notion of Entanglement
Motivated by the novel applications of the mathematical formalism of quantum
theory and its generalizations in cognitive science, psychology, social and
political sciences, and economics, we extend the notion of the tensor product
and entanglement. We also study the relation between conventional entanglement
of complex qubits and our generalized entanglement. Our construction can also
be used to describe entanglement in the framework of non-Archimedean physics.
It is also possible to construct tensor products of non-Archimedean (e.g.,
-adic) and complex Hilbert spaces.Comment: Proceedings of AIP, conference Foundations of Probability and Physics
6, Vaxjo, Sweden, June 2011, volume 142
Transition Temperature of Dilute, Weakly Repulsive Bose Gas
Within a quasiparticle framework, we reconsider the issue of computing the
Bose-Einstein condensation temperature () in a weakly non-ideal Bose gas.
The main result of this and previous investigations is that increases
with the scattering length , with the leading dependence being either linear
or log-linear in . The calculation of reduces to that of computing the
excitation spectrum near the transition. We report two approaches to
regularizing the infrared divergence at the transition point. One leads to a
-like shift in , and the other allows numerical
calculations for the shift.Comment: 8 pages, 3 figures, revtex
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