1,195,830 research outputs found
DRA method: Powerful tool for the calculation of the loop integrals
We review the method of the calculation of multiloop integrals suggested in
Ref.\cite{Lee2010}.Comment: 6 pages, contribution to ACAT2011 proceedings, Uxbridge, London,
September 5-9, 2011, typos are correcte
Transverse Spin: HERMES Results and Future Plans
Results from the HERMES experiment are presented on single-spin asymmetries
in semi-inclusive hadron production from longitudinally polarized targets. The
data are compared with a number of theoretical calculations which relate the
azimuthal dependence of the asymmetries to the transversity structure function
h_1(x).Comment: 9 pages, 4 figures requiring 9 EPS files, contribution to the
European Workshop On The QCD Structure Of The Nucleon (QCD-N'02), to be
published in Nucl. Phys.
Implications of Flavored CP Symmetry of Leptons
We discuss gauge models incorporating flavored CP symmetry (called
CP in the text) in combination with invariance to
understand neutrino mixings and discuss their phenomenological implications. We
show that viable leptogenesis in this setting requires that the lightest
right-handed neutrino mass must be between GeV and for effective
two hierarchical right-handed neutrinos, leptogenesis takes place only in a
narrower range of GeV. A multi-Higgs realization of
this idea implies that there must be a pseudoscalar Higgs boson with mass less
than 300 GeV. Generically, the vev alignment problem can be naturally avoided
in our setting.Comment: 34pp. v3: matches journal versio
The Free Energy of N=4 Super-Yang-Mills and the AdS/CFT Correspondence
We compute the high-temperature limit of the free energy for four-dimensional
N=4 supersymmetric SU(N_c) Yang-Mills theory. At weak coupling we do so for a
general ultrastatic background spacetime, and in the presence of slowly-varying
background gauge fields. Using Maldacena's conjectured duality, we calculate
the strong-coupling large-N_c expression for the special case that the
three-space has constant curvature. We compare the two results paying
particular attention to curvature corrections to the leading order expressions.Comment: 26 pages.Minor corrections to eqs.(19),(21). Results and conclusions
unchanged. References adde
Complementarity of perturbations driving insulator-to-metal transition in a charge ordered manganite
Modulation of charge carrier dynamics and hence electrical conductivity of
solids by photoexcitation has been a rich field of research with numerous
applications. Similarly, electric and magnetic field assisted enhancement of
conductivity are of fundamental importance and technological use. Hole doped
manganites of the type (ABMnO, where A and B are rare and
alkaline earth metals respectively have the distinction of showing all three
effects. Here we establish the complementarity of the electric, magnetic and
photon fields in driving an insulator-metal transition in epitaxial thin films
of LaPrCaMnO whose electrical ground state
is insulating. Both pulsed and CW lasers cause a giant photon flux dependent
enhancement of conductivity. It is further observed that electric and magnetic
fields trigger the persistent enhancement of conductivity whose magnitude can
be accentuated by application of these fields in parallel.Comment: 17 pages 6 figure
Fractional Branes and the Entropy of 4D Black Holes
We reconsider the four dimensional extremal black hole constructed in type
IIB string theory as the bound state of D1-branes, D5-branes, momentum, and
Kaluza-Klein monopoles. Specifically, we examine the case of an arbitrary
number of monopoles. Consequently, the weak coupling calculation of the
microscopic entropy requires a study of the D1-D5 system on an ALE space. We
find that the complete expression for the Bekenstein-Hawking entropy is
obtained by taking into account the massless open strings stretched between the
fractional D-branes which arise in the orbifold limit of the ALE space. The
black hole sector therefore arises as a mixed Higgs-Coulomb branch of an
effective 1+1 dimensional gauge theory.Comment: 12 pages. 1 figure. v2: References adde
Electronic oscillations in paired polyacetylene chains
An interacting pair of polyacetylene chains are initially modeled as a couple
of undimerized polymers described by a Hamiltonian based on the tight-binding
model representing the electronic behavior along the linear chain, plus a
Dirac's potential double well representing the interaction between the chains.
A theoretical field formalism is employed, and we find that the system exhibits
a gap in its energy band due to the presence of a mass-matrix term in the
Dirac's Lagrangian that describes the system. The Peierls instability is
introduced in the chains by coupling a scalar field to the fermions of the
theory via spontaneous symmetry breaking, to obtain a kink-like soliton, which
separates two vacuum regions, i.e., two spacial configurations (enantiomers) of
the each molecule. Since that mass-matrix and the pseudo-spin operator do not
commute in the same quantum representation, we demonstrate that there is a
particle oscillation phenomenon with a periodicity equivalent to the Bloch
oscillations.Comment: 4 pages, 1 figure.to appear in Solid State Communication
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