697 research outputs found
Absence of Nonlocal Counter-terms in the Gauge Boson Propagator in Axial -type Gauges
We study the two-point function for the gauge boson in the axial-type gauges.
We use the exact treatment of the axial gauges recently proposed that is
intrinsically compatible with the Lorentz type gauges in the path-integral
formulation and has been arrived at from this connection and which is a
``one-vector'' treatment. We find that in this treatment, we can evaluate the
two-point functions without imposing any additional interpretation on the axial
gauge 1/(n.q)^p-type poles. The calculations are as easy as the other
treatments based on other known prescriptions. Unlike the
``uniform-prescription'' /L-M prescription, we note, here, the absence of any
non-local divergences in the 2-point proper vertex. We correlate our
calculation with that for the Cauchy Principal Value prescription and find from
this comparison that the 2-point proper vertex differs from the CPV calculation
only by finite terms. For simplicity of treatment, the divergences have been
calculated here with n^2>0 and these have a smooth light cone limit.Comment: 17 pages; 3 figures drawn using feyn.st
Validating Hypothetical Surveys Using Binding Public Referenda: Implications for Stated Preference Valuation
This study presents a criterion validity test in which stated choices are compared to subsequent binding referendum votes. The study is distinguished by identical hypothetical and actual choice contexts, and results that show no evidence of hypothetical bias. Results suggest a number of possibilities for amelioration of hypothetical bias.Research Methods/ Statistical Methods,
Understanding of the Renormalization Program in a mathematically Rigorous Framework and an Intrinsic Mass Scale
we show there exists a mathematically consistent framework in which the
Renormalization Program can be understood in a natural manner. The framework
does not require any violations of mathematical rigor usually associated with
the Renormalization program. We use the framework of the non-local field
theories [these carry a finite mass scale (\Lambda)]and set up a finite
perturbative program. We show how this program leads to the perturbation series
of the usual renormalization program [except one difference] if the series is
restructured .We further show that the comparison becomes possible if there
exists a finite mass scale (\Lambda), with certain properties, in the Quantum
Field theory [which we take to be the scale present in the nonlocal theory]. We
give a way to estimate the scale (\Lambda). We also show that the finite
perturbation program differs from the usual renormalization program by a term;
which we propose can also be used to put a bound on (\Lambda).Comment: 19 pages, a missing equation added,a reference added and a few typos
correcte
Scientific Publications: Methods and Skills Workshop, C-DAC Conference Hall, University of Pune, Pune, India, November 9, 2006
Mapping between Hamiltonians with attractive and repulsive potentials on a lattice
Through a simple and exact analytical derivation, we show that for a particle
on a lattice, there is a one-to-one correspondence between the spectra in the
presence of an attractive potential and its repulsive counterpart
. For a Hermitian potential, this result implies that the number of
localized states is the same in both, attractive and repulsive, cases although
these states occur above (below) the band-continnum for the repulsive
(attractive) case. For a \mP\mT-symmetric potential that is odd under parity,
our result implies that in the \mP\mT-unbroken phase, the energy eigenvalues
are symmetric around zero, and that the corresponding eigenfunctions are
closely related to each other.Comment: 6 pages, 1 figur
Wilson Loop and the Treatment of Axial Gauge Poles
We consider the question of gauge invariance of the Wilson loop in the light
of a new treatment of axial gauge propagator proposed recently based on a
finite field-dependent BRS (FFBRS) transformation. We remark that as under the
FFBRS transformation the vacuum expectation value of a gauge invariant
observable remains unchanged, our prescription automatically satisfies the
Wilson loop criterion. Further, we give an argument for {\it direct}
verification of the invariance of Wilson loop to O(g^4) using the earlier work
by Cheng and Tsai. We also note that our prescription preserves the thermal
Wilson loop to O(g^2).Comment: 8 pages, LaTex; some typos related to equation (18) correcte
Superfield approach to symmetry invariance in QED with complex scalar fields
We show that the Grassmannian independence of the super Lagrangian density,
expressed in terms of the superfields defined on a (4, 2)-dimensional
supermanifold, is a clear-cut proof for the Becchi-Rouet-Stora-Tyutin (BRST)
and anti-BRST invariance of the corresoponding four (3 + 1)-dimensional (4D)
Lagrangian density that describes the interaction between the U(1) gauge field
and the charged complex scalar fields. The above 4D field theoretical model is
considered on a (4, 2)-dimensional supermanifold parametrized by the ordinary
four spacetime variables x^\mu (with \mu = 0, 1, 2, 3) and a pair of
Grassmannian variables \theta and \bar\theta (with \theta^2 = \bar\theta^2 = 0,
\theta \bar\theta + \bar\theta \theta = 0). Geometrically, the (anti-)BRST
invariance is encoded in the translation of the super Lagrangian density along
the Grassmannian directions of the above supermanifold such that the outcome of
this shift operation is zero.Comment: LaTeX file, 14 pages, minor changes in the title and text, version to
appear in ``Pramana - Journal of Physics'
Absence of Wigner Crystallization in Graphene
Graphene, a single sheet of graphite, has attracted tremendous attention due
to recent experiments which demonstrate that carriers in it are described by
massless fermions with linear dispersion. In this note, we consider the
possibility of Wigner crystallization in graphene in the absence of external
magnetic field. We show that the ratio of potential and kinetic energy is
independent of the carrier density, the tuning parameter that usually drives
Wigner crystallization and find out that for given material parameters
(dielectric constant and Fermi velocity), Wigner crystallization is not
possible. We comment on the how these results change in the presence of a
strong external magnetic field.Comment: 3 pages, 1 figure,Submitted for PR
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