831 research outputs found
Jacobian of meromorphic curves
The contact structure of two meromorphic curves gives a factorization of
their jacobian.Comment: 41 pages, amstex, to be published in the Proceedings of the Indian
Academy of Science
Worldsheet Realization of the Refined Topological String
A worldsheet realization of the refined topological string is proposed in
terms of physical string amplitudes that compute generalized N=2 F-terms of the
form F_{g,n} W^{2g}Y^{2n} in the effective supergravity action. These terms
involve the chiral Weyl superfield W and a superfield Y defined as an N=2
chiral projection of a particular anti-chiral T-bar vector multiplet. In
Heterotic and Type I theories, obtained upon compactification on the
six-dimensional manifold K3xT2, T is the usual K\"ahler modulus of the T2
torus. These amplitudes are computed exactly at the one-loop level in string
theory. They are shown to reproduce the correct perturbative part of the
Nekrasov partition function in the field theory limit when expanded around an
SU(2) enhancement point of the string moduli space. The two deformation
parameters epsilon_- and epsilon_+ of the Omega-supergravity background are
then identified with the constant field-strength backgrounds for the
anti-self-dual graviphoton and self-dual gauge field of the T-bar vector
multiplet, respectively.Comment: 35 pages, typos corrected, published in NP
Non-Perturbative Nekrasov Partition Function from String Theory
We calculate gauge instanton corrections to a class of higher derivative
string effective couplings introduced in [1]. We work in Type I string theory
compactified on K3xT2 and realise gauge instantons in terms of D5-branes
wrapping the internal space. In the field theory limit we reproduce the
deformed ADHM action on a general {\Omega}-background from which one can
compute the non-perturbative gauge theory partition function using
localisation. This is a non-perturbative extension of [1] and provides further
evidence for our proposal of a string theory realisation of the
{\Omega}-background.Comment: 23 page
Probing the Moduli Dependence of Refined Topological Amplitudes
With the aim of providing a worldsheet description of the refined topological
string, we continue the study of a particular class of higher derivative
couplings in the type II string effective action compactified on a
Calabi-Yau threefold. We analyse first order differential equations in the
anti-holomorphic moduli of the theory, which relate the to other
component couplings. From the point of view of the topological theory, these
equations describe the contribution of non-physical states to twisted
correlation functions and encode an obstruction for interpreting the
as the free energy of the refined topological string theory. We investigate
possibilities of lifting this obstruction by formulating conditions on the
moduli dependence under which the differential equations simplify and take the
form of generalised holomorphic anomaly equations. We further test this
approach against explicit calculations in the dual heterotic theory.Comment: 30 page
Optimizing the method for authenticating pharmaceutical products of different dosage forms using dual laser handheld raman spectroscopy
Handheld Raman spectroscopy has emerged over the last few years as a rapid technique for authenticating medicines. Major challenges arose in the authentication process attributed to the Raman activity of the main constituents or to the formulation type. This witnessed the masking of the Raman signal of herbal medicinal products or medicinal products of low dosage forms. Liquid and semisolid formulations represented a further challenge in the authentication process which was mainly attributed to the number of soluble/insoluble constituents. The present work aims to optimize the method for authenticating medicinal products of different dosage forms using dual laser handheld Raman spectroscopy
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