96 research outputs found
Scaling critical behavior of superconductors at zero magnetic field
We consider the scaling behavior in the critical domain of superconductors at
zero external magnetic field. The first part of the paper is concerned with the
Ginzburg-Landau model in the zero magnetic field Meissner phase. We discuss the
scaling behavior of the superfluid density and we give an alternative proof of
Josephson's relation for a charged superfluid. This proof is obtained as a
consequence of an exact renormalization group equation for the photon mass. We
obtain Josephson's relation directly in the form , that
is, we do not need to assume that the hyperscaling relation holds. Next, we
give an interpretation of a recent experiment performed in thin films of
. We argue that the measured mean field like
behavior of the penetration depth exponent is possibly associated with a
non-trivial critical behavior and we predict the exponents and
for the correlation lenght and specific heat, respectively. In the
second part of the paper we discuss the scaling behavior in the continuum dual
Ginzburg-Landau model. After reviewing lattice duality in the Ginzburg-Landau
model, we discuss the continuum dual version by considering a family of
scalings characterized by a parameter introduced such that
, where is the bare mass of the magnetic
induction field. We discuss the difficulties in identifying the renormalized
magnetic induction mass with the photon mass. We show that the only way to have
a critical regime with is having , that
is, with having the scaling behavior of the renormalized photon mass.Comment: RevTex, 15 pages, no figures; the subsection III-C has been removed
due to a mistak
Towards Higgs boson production in gluon fusion to NNLO in the MSSM
We consider the Higgs boson production in the gluon-fusion channel to
next-to-next-to-leading order within the Minimal Supersymmetric Standard Model.
In particular, we present analytical results for the matching coefficient of
the effective theory and study its influence on the total production cross
section in the limit where the masses of all MSSM particles coincide. For
supersymmetric masses below 500 GeV it is possible to find parameters leading
to a significant enhancement of the Standard Model cross section, the
-factors, however, change only marginally.Comment: 20 pages; v2: modification of discussion of numerical effect, version
to appear in EPJC; v3: eq.(18) corrected, minor correction
Symmetry Nonrestoration in a Gross-Neveu Model with Random Chemical Potential
We study the symmetry behavior of the Gross-Neveu model in three and two
dimensions with random chemical potential. This is equivalent to a four-fermion
model with charge conjugation symmetry as well as Z_2 chiral symmetry. At high
temperature the Z_2 chiral symmetry is always restored. In three dimensions the
initially broken charge conjugation symmetry is not restored at high
temperature, irrespective of the value of the disorder strength. In two
dimensions and at zero temperature the charge conjugation symmetry undergoes a
quantum phase transition from a symmetric state (for weak disorder) to a broken
state (for strong disorder) as the disorder strength is varied. For any given
value of disorder strength, the high-temperature behavior of the charge
conjugation symmetry is the same as its zero-temperature behavior. Therefore,
in two dimensions and for strong disorder strength the charge conjugation
symmetry is not restored at high temperature.Comment: 16 pages, 3 figure
Two-Loop Helicity Amplitudes for Quark-Gluon Scattering in QCD and Gluino-Gluon Scattering in Supersymmetric Yang-Mills Theory
We present the two-loop QCD helicity amplitudes for quark-gluon scattering,
and for quark-antiquark annihilation into two gluons. These amplitudes are
relevant for next-to-next-to-leading order corrections to (polarized) jet
production at hadron colliders. We give the results in the `t Hooft-Veltman and
four-dimensional helicity (FDH) variants of dimensional regularization. The
transition rules for converting the amplitudes between the different variants
are much more intricate than for the previously discussed case of gluon-gluon
scattering. Summing our two-loop expressions over helicities and colors, and
converting to conventional dimensional regularization, gives results in
complete agreement with those of Anastasiou, Glover, Oleari and Tejeda-Yeomans.
We describe the amplitudes for 2 to 2 scattering in pure N=1 supersymmetric
Yang-Mills theory, obtained from the QCD amplitudes by modifying the color
representation and multiplicities, and verify supersymmetry Ward identities in
the FDH scheme.Comment: 77 pages. v2: corrected errors in eqs. (3.7) and (3.8) for one-loop
assembly; remaining results unaffecte
Economic analysis of an agrosilvipastoral system for a mountainous area in Zona da Mata Mineira, Brazil
Chemical similarity among domesticated and wild genotypes of peanut based on n-alkanes profiles
RI'/SMOM scheme amplitudes for quark currents at two loops
We determine the two loop corrections to the Green's function of a quark
current inserted in a quark 2-point function at the symmetric subtraction
point. The amplitudes for the scalar, vector and tensor currents are presented
in both the MSbar and RI'/SMOM renormalization schemes. The RI'/SMOM scheme two
loop renormalization for the scalar and tensor cases agree with previous work.
The vector current renormalization requires special treatment as it must be
consistent with the Slavnov-Taylor identity which we demonstrate. We also
discuss the possibility of an alternative definition of the RI'/SMOM scheme in
the case of the tensor current.Comment: 36 latex pages, 1 figure, 21 tables, anc directory contains txt file
with data in table
Characterization and nutrient release from silicate rocks and influence on chemical changes in soil
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