12,930 research outputs found
Evidence for multiple superconducting gaps in optimally doped BaFeCoAs from infrared spectroscopy
We performed combined infrared reflection and ellipsometry measurements of
the in-plane optical reponse of single crystals of the pnictide high
temperature superconductor BaFeCoAs with = 24.5
K. We observed characteristic superconductivity-induced changes which provide
evidence for at least three different energy gaps. We show that a BCS-model of
isotropic gaps with 2 of 3.1, 4.7, and 9.2 reproduces the
experimental data rather well. We also determine the low-temperature value of
the in-plane magnetic penetration depth of 270 nm
Superfield Approach to (Non-)local Symmetries for One-Form Abelian Gauge Theory
We exploit the geometrical superfield formalism to derive the local,
covariant and continuous Becchi-Rouet-Stora-Tyutin (BRST) symmetry
transformations and the non-local, non-covariant and continuous dual-BRST
symmetry transformations for the free Abelian one-form gauge theory in four -dimensions (4D) of spacetime. Our discussion is carried out in the
framework of BRST invariant Lagrangian density for the above 4D theory in the
Feynman gauge. The geometrical origin and interpretation for the (dual-)BRST
charges (and the transformations they generate) are provided in the language of
translations of some superfields along the Grassmannian directions of the six
(-dimensional supermanifold parametrized by the four spacetime and two
Grassmannian variables.Comment: LaTeX file, 23 page
Gauge Transformations, BRST Cohomology and Wigner's Little Group
We discuss the (dual-)gauge transformations and BRST cohomology for the two
(1 + 1)-dimensional (2D) free Abelian one-form and four (3 + 1)-dimensional
(4D) free Abelian 2-form gauge theories by exploiting the (co-)BRST symmetries
(and their corresponding generators) for the Lagrangian densities of these
theories. For the 4D free 2-form gauge theory, we show that the changes on the
antisymmetric polarization tensor e^{\mu\nu} (k) due to (i) the (dual-)gauge
transformations corresponding to the internal symmetry group, and (ii) the
translation subgroup T(2) of the Wigner's little group, are connected with
each-other for the specific relationships among the parameters of these
transformation groups. In the language of BRST cohomology defined w.r.t. the
conserved and nilpotent (co-)BRST charges, the (dual-)gauge transformed states
turn out to be the sum of the original state and the (co-)BRST exact states. We
comment on (i) the quasi-topological nature of the 4D free 2-form gauge theory
from the degrees of freedom count on e^{\mu\nu} (k), and (ii) the Wigner's
little group and the BRST cohomology for the 2D one-form gauge theory {\it
vis-{\`a}-vis} our analysis for the 4D 2-form gauge theory.Comment: LaTeX file, 29 pages, misprints in (3.7), (3.8), (3.9), (3.13) and
(4.14)corrected and communicated to IJMPA as ``Erratum'
Nilpotent Symmetries For Matter Fields In Non-Abelian Gauge Theory: Augmented Superfield Formalism
In the framework of superfield approach to Becchi-Rouet-Stora-Tyutin (BRST)
formalism, the derivation of the (anti-)BRST nilpotent symmetries for the
matter fields, present in any arbitrary interacting gauge theory, has been a
long-standing problem. In our present investigation, the local, covariant,
continuous and off-shell nilpotent (anti-)BRST symmetry transformations for the
Dirac fields are derived in the framework of the augmented
superfield formulation where the four -dimensional (4D) interacting
non-Abelian gauge theory is considered on the six -dimensional
supermanifold parametrized by the four even spacetime coordinates and a
couple of odd elements ( and ) of the Grassmann algebra.
The requirement of the invariance of the matter (super)currents and the
horizontality condition on the (super)manifolds leads to the derivation of the
nilpotent symmetries for the matter fields as well as the gauge- and the
(anti-)ghost fields of the theory in the general scheme of the augmented
superfield formalism.Comment: LaTeX file, 16 pages, printing mistakes in the second paragraph of
`Introduction' corrected, a footnote added, these modifications submitted as
``erratum'' to IJMPA in the final for
Eigenvalue spectrum for single particle in a spheroidal cavity: A Semiclassical approach
Following the semiclassical formalism of Strutinsky et al., we have obtained
the complete eigenvalue spectrum for a particle enclosed in an infinitely high
spheroidal cavity. Our spheroidal trace formula also reproduces the results of
a spherical billiard in the limit . Inclusion of repetition of each
family of the orbits with reference to the largest one significantly improves
the eigenvalues of sphere and an exact comparison with the quantum mechanical
results is observed upto the second decimal place for . The
contributions of the equatorial, the planar (in the axis of symmetry plane) and
the non-planar(3-Dimensional) orbits are obtained from the same trace formula
by using the appropriate conditions. The resulting eigenvalues compare very
well with the quantum mechanical eigenvalues at normal deformation. It is
interesting that the partial sum of equatorial orbits leads to eigenvalues with
maximum angular momentum projection, while the summing of planar orbits leads
to eigenvalues with except for L=1. The remaining quantum mechanical
eigenvalues are observed to arise from the 3-dimensional(3D) orbits. Very few
spurious eigenvalues arise in these partial sums. This result establishes the
important role of 3D orbits even at normal deformations.Comment: 17 pages, 7 ps figure
Magnetic and Transport Properties of Ternary Indides of type R2CoIn8 (R = Ce, Pr and Dy)
We have synthesized and investigated the magnetic and transport properties of
a series of compounds, R2CoIn8 (R = rare earth). Compounds form in single phase
with a tetragonal structure (space group P4/mmm, no. 162). The Ce compound
shows heavy fermion behavior. The magnetic susceptibility of Pr2CoIn8 shows a
marked deviation from the Curie-Weiss behavior at low temperatures, which is
attributed to the crystalline electric field effects. Heat capacity and
magnetization measurements show that Dy2CoIn8 undergoes a magnetic transition
at 17 K and a second transition near 5 K, the latter of which may be due to
spin reorientation. Magnetization of this compound shows two metamagnetic
transitions approximately at 3.6 T and 8.3 T.Comment: Total 7 pages of text and figure
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