19,279 research outputs found
Non-local Wess-Zumino Model on Nilpotent Noncommutative Superspace
We investigate the theory of the bosonic-fermionic noncommutativity,
, and the Wess-Zumino model
deformed by the noncommutativity. Such noncommutativity links well-known
space-time noncommutativity to superspace non-anticommutativity. The
deformation has the nilpotency. We can explicitly evaluate noncommutative
effect in terms of new interactions between component fields. The interaction
terms that have Grassmann couplings are induced. The noncommutativity does
completely break full supersymmetry to
theory in Minkowski signature. Similar to the space-time noncommutativity, this
theory has higher derivative terms and becomes non-local theory. However this
non-locality is milder than the space-time noncommutative field theory. Due to
the nilpotent feature of the coupling constants, we find that there are only
finite number of Feynman diagrams that give noncommutative corrections at each
loop order.Comment: Latex, 16 pages, 2 figures, typos corrected, some references and
comments on auxiliary field added, a figure replaced, English refine
Scaling Analysis of Domain-Wall Free-Energy in the Edwards-Anderson Ising Spin Glass in a Magnetic Field
The stability of the spin-glass phase against a magnetic field is studied in
the three and four dimensional Edwards-Anderson Ising spin glasses. Effective
couplings and effective fields associated with length scale L are measured by a
numerical domain-wall renormalization group method. The results obtained by
scaling analysis of the data strongly indicate the existence of a crossover
length beyond which the spin-glass order is destroyed by field H. The crossover
length well obeys a power law of H which diverges as H goes to zero but remains
finite for any non-zero H, implying that the spin-glass phase is absent even in
an infinitesimal field. These results are well consistent with the droplet
theory for short-range spin glasses.Comment: 4 pages, 5 figures; The text is slightly changed, the figures 3, 4
and 5 are changed, and a few references are adde
Virtual photon structure functions and positivity constraints
We study the three positivity constraints among the eight virtual photon
structure functions, derived from the Cauchy-Schwarz inequality and which are
hence model-independent. The photon structure functions obtained from the
simple parton model show quite different behaviors in a massive quark or a
massless quark case, but they satisfy, in both cases, the three positivity
constraints. We then discuss an inequality which holds among the unpolarized
and polarized photon structure functions , and
, in the kinematic region , where is the mass squared of the probe (target) photon, and we examine
whether this inequality is satisfied by the perturbative QCD results.Comment: 24 pages, 13 eps figure
Competition between Charge Ordering and Superconductivity in Layered Organic Conductors -(BEDT-TTF)Hg(SCN) (M = K, NH)
While the optical properties of the superconducting salt
-(BEDT-TTF)NHHg(SCN) remain metallic down to 2 K, in the
non-superconducting K-analog a pseudogap develops at frequencies of about 200
cm for temperatures T < 200 K. Based on exact diagonalisation
calculations on an extended Hubbard model at quarter-filling we argue that
fluctuations associated with short range charge ordering are responsible for
the observed low-frequency feature. The different ground states, including
superconductivity, are a consequence of the proximity of these compounds to a
quantum phase charge-ordering transition driven by the intermolecular Coulomb
repulsion.Comment: 4 pages, 3 figure
Metal-insulator transition and the Pr/Pr valence shift in (PrY)CaCoO
The magnetic, electric and thermal properties of the
(Y)CaCoO perovskites (~=~Pr, Nd) were
investigated down to very low temperatures. The main attention was given to a
peculiar metal-insulator transition, which is observed in the praseodymium
based samples with and 0.15 at and 132~K, respectively.
The study suggests that the transition, reported originally in
PrCaCoO, is not due to a mere change of cobalt ions from
the intermediate- to the low-spin states, but is associated also with a
significant electron transfer between Pr and Co/Co sites,
so that the praseodymium ions occur below in a mixed
Pr/Pr valence. The presence of Pr ions in the insulating
phase of the yttrium doped samples (PrY)CaCoO
is evidenced by Schottky peak originating in Zeeman splitting of the ground
state Kramers doublet. The peak is absent in pure PrCaCoO
in which metallic phase, based solely on non-Kramers Pr ions, is
retained down to the lowest temperature.Comment: 10 figure
Dropping rho and A_1 Meson Masses at Chiral Phase Transition in the Generalized Hidden Local Symmetry
We study the chiral symmetry restoration using the generalized hidden local
symmetry (GHLS) which incorporates the rho and A_1 mesons as the gauge bosons
of the GHLS and the pion as the Nambu-Goldstone boson consistently with the
chiral symmetry of QCD. We show that a set of parameter relations, which
ensures the first and second Weinberg's sum rules, is invariant under the
renormalization group evolution. Then, we found that the Weinberg's sum rules
together with the matching of the vector and axial-vector current correlators
inevitably leads to {\it the dropping masses of both rho and A_1 mesons} at the
symmetry restoration point, and that the mass ratio as well as the mixing angle
between the pion and A_1 meson flows into one of three fixed points.Comment: 17 pages, 7 figures; references added and discussions expande
Disorder chaos in spin glasses
We investigate numerically disorder chaos in spin glasses, i.e. the
sensitivity of the ground state to small changes of the random couplings. Our
study focuses on the Edwards-Anderson model in d=1,2,3 and in mean-field. We
find that in all cases, simple scaling laws, involving the size of the system
and the strength of the perturbation, are obeyed. We characterize in detail the
distribution of overlap between ground states and the geometrical properties of
flipped spin clusters in both the weak and strong chaos regime. The possible
relevance of these results to temperature chaos is discussed.Comment: 7 pages, 8 figures, replaced with accepted versio
Dynamics of bubbles in a two-component Bose-Einstein condensate
The dynamics of a phase-separated two-component Bose-Einstein condensate are
investigated, in which a bubble of one component moves through the other
component. Numerical simulations of the Gross--Pitaevskii equation reveal a
variety of dynamics associated with the creation of quantized vortices. In two
dimensions, a circular bubble deforms into an ellipse and splits into fragments
with vortices, which undergo the Magnus effect. The B\'enard--von K\'arm\'an
vortex street is also generated. In three dimensions, a spherical bubble
deforms into toruses with vortex rings. When two rings are formed, they exhibit
leapfrogging dynamics.Comment: 6 pages, 7 figure
Wind-generated power input to the deep ocean: An estimate using a (1)/(10)degrees general circulation model
- âŠ