Ghanashyam Date | The Institute of Mathematical Sciences, Chennai (original) (raw)
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Papers by Ghanashyam Date
Institute of Mathematical Sciences eBooks, 1997
These are the proceedings of the XVIII Conference of the Indian Association for General Relativit... more These are the proceedings of the XVIII Conference of the Indian Association for General Relativity and Gravitation (IAGRG) held at the Institute of Mathematical Sciences, Madras, INDIA during Feb. 15-17, 1996. The Conference was dedicated the late Prof. S. Chandrasekhar. The proceedings consists of 17 articles on: - Chandrasekhar's work (N. Panchapkesan); - Vaidya-Raychaudhuri Lecture (C.V. Vishveshwara) - Gravitational waves (B.R. Iyer, R. Balasubramanian) - Gravitational Collapse (T.P. Singh) - Accretion on black hole (S. Chakrabarti) - Cosmology (D. Munshi, S. Bharadwaj, G.S. Mohanty, P. Bhattacharjee); - Classical GR (S. Kar, D.C. Srivatsava) - Quantum aspects (J. Maharana, Saurya Das, P. Mitra, G. Date, N.D. Hari Dass) The body of THIS article contains ONLY the title, contents, foreword, organizing committees, preface, list of contributed talks and list of participants. The plenery talks are available at: http://www.imsc.ernet.in/physweb/Conf/ both as post-script files of individual articles and also as .uu source files. For further information please send e-mail to shyam@imsc.ernet.in
Physical review, Feb 6, 2009
We set up a canonical Hamiltonian formulation for a theory of gravity based on a Lagrangian densi... more We set up a canonical Hamiltonian formulation for a theory of gravity based on a Lagrangian density made up of the Hilbert-Palatini term and, instead of the Holst term, the Nieh-Yan topological density. The resulting set of constraints in the time gauge are shown to lead to a theory in terms of a real SU (2) connection which is exactly the same as that of Barbero and Immirzi with the coefficient of the Nieh-Yan term identified as the inverse of Barbero-Immirzi parameter. This provides a topological interpretation for this parameter. Matter coupling can then be introduced in the usual manner, without changing the universal topological Nieh-Yan term.
Physical Review A, 1993
In this paper we show that (a) all the known exact solutions of the problem of Nanyons in oscilla... more In this paper we show that (a) all the known exact solutions of the problem of Nanyons in oscillator potential precisely arise from the collective degrees of freedom, (b) the system is pseudo-integrable ala Richens and Berry. We conclude that the exact solutions are trivial thermodynamically as well as dynamically.
arXiv (Cornell University), Apr 17, 2010
arXiv (Cornell University), Jul 5, 2022
These are lecture notes of the QFT-I course I gave in an online mode at Chennai Mathematical Inst... more These are lecture notes of the QFT-I course I gave in an online mode at Chennai Mathematical Institute. The course focussed on the free relativistic quantum fields, their interactions in the perturbative scattering framework, standard computations of QED processes, radiative corrections at 1-loop with renormalization and an introduction to the toolbox of path integrals.
General Relativity and Gravitation, 1997
Einstein equations with T µν = k µ k ν + ℓ µ ℓ ν where k, ℓ are null are considered with spherica... more Einstein equations with T µν = k µ k ν + ℓ µ ℓ ν where k, ℓ are null are considered with spherical symmetry and staticity. The solution has naked singularity and is not asymptotically flat. However, it may be interpreted as an envelope for any static spherical body making it more massive. Such an interpretation and some of its implications are detailed.
Since the past Iagrg meeting in December 2004, new developments in loop quantum cosmology have ta... more Since the past Iagrg meeting in December 2004, new developments in loop quantum cosmology have taken place, especially with regards to the resolution of the Big Bang singularity in the isotropic models. The singularity resolution issue has been discussed in terms of physical quantities (expectation values of Dirac observables) and there is also an ``improved'' quantization of the Hamiltonian constraint. These developments are briefly discussed. This is an expanded version of the review talk given at the 24$^{\mathrm{th}}$ IAGRG meeting in February 2007.
Fermions constitute an important component of matter and their quantization in presence of dynami... more Fermions constitute an important component of matter and their quantization in presence of dynamical gravity is essential for any theory of quantum gravity. We revisit the classical formulation adapted for a background free quantization. The analysis is carried out with the Hilbert-Palatini form for gravity together with the Nieh-Yan topological term which keeps the nature of Barbero-Immirzi parameter independent of inclusion of arbitrary matter with arbitrary couplings. With dynamical gravity, a priori, there are two distinct notions of `parity' - orientation reversing diffeomorphisms and improper Lorentz rotations. The invariance properties of the action and the canonical framework are different with respect to these and gravitational origin of parity violation seems ambiguous.
Pramana, 2004
This is a written, expanded version of the summary talk given at the conclusion of the ICGC-2004 ... more This is a written, expanded version of the summary talk given at the conclusion of the ICGC-2004 held at Cochin. Brief introductory remarks are included to provide a slightly wider context to the theme talks.
Physics Letters B, 1983
Abstract A general framework is developed to analyse the influence of soft partons on the high en... more Abstract A general framework is developed to analyse the influence of soft partons on the high energy behaviour of the Drell-Yan cross section.
Physical Review D, 2005
Loop quantization of diagonalized Bianchi class A models, leads to a partial difference equation ... more Loop quantization of diagonalized Bianchi class A models, leads to a partial difference equation as the Hamiltonian constraint at the quantum level. A criterion for testing a viable semiclassical limit has been formulated in terms of existence of the so-called pre-classical solutions. We demonstrate the existence of pre-classical solutions of the quantum equation for the vacuum Bianchi I model. All these solutions avoid the classical singularity at vanishing volume.
Physical Review D, 2005
In classical general relativity, the generic approach to the initial singularity is usually under... more In classical general relativity, the generic approach to the initial singularity is usually understood in terms of the BKL scenario. In this scenario, along with the Bianchi IX model, the exact, singular, Kasner solution of vacuum Bianchi I model also plays a pivotal role. Using an effective classical Hamiltonian obtained from loop quantization of vacuum Bianchi I model, exact solution is obtained which is non-singular due to a discreteness parameter. The solution is parameterized in exactly the same manner as the usual Kasner solution and reduces to the Kasner solution as discreteness parameter is taken to zero. At the effective Hamiltonian level, the avoidance of Kasner singularity uses a mechanism distinct from the 'inverse volume' modifications characteristic of loop quantum cosmology.
Physical Review D, 1983
An alternate and more general form of factorization for the Drell-Yan process is derived in pertu... more An alternate and more general form of factorization for the Drell-Yan process is derived in perturbation theory. Corresponding generalized anomalous dimensions are defined. Simple calculations verify Mueller's conjecture for the recovery of improved parton-model results at very high energies. The approach offers a general framework to analyze the role played by soft partons, and to study their influence on asymptotic behavior.
Modern Physics Letters A, 2002
This is a review talk describing the recent work of Martin Bojowald on Loop Quantum Cosmology.
Institute of Mathematical Sciences eBooks, 1997
These are the proceedings of the XVIII Conference of the Indian Association for General Relativit... more These are the proceedings of the XVIII Conference of the Indian Association for General Relativity and Gravitation (IAGRG) held at the Institute of Mathematical Sciences, Madras, INDIA during Feb. 15-17, 1996. The Conference was dedicated the late Prof. S. Chandrasekhar. The proceedings consists of 17 articles on: - Chandrasekhar's work (N. Panchapkesan); - Vaidya-Raychaudhuri Lecture (C.V. Vishveshwara) - Gravitational waves (B.R. Iyer, R. Balasubramanian) - Gravitational Collapse (T.P. Singh) - Accretion on black hole (S. Chakrabarti) - Cosmology (D. Munshi, S. Bharadwaj, G.S. Mohanty, P. Bhattacharjee); - Classical GR (S. Kar, D.C. Srivatsava) - Quantum aspects (J. Maharana, Saurya Das, P. Mitra, G. Date, N.D. Hari Dass) The body of THIS article contains ONLY the title, contents, foreword, organizing committees, preface, list of contributed talks and list of participants. The plenery talks are available at: http://www.imsc.ernet.in/physweb/Conf/ both as post-script files of individual articles and also as .uu source files. For further information please send e-mail to shyam@imsc.ernet.in
Physical review, Feb 6, 2009
We set up a canonical Hamiltonian formulation for a theory of gravity based on a Lagrangian densi... more We set up a canonical Hamiltonian formulation for a theory of gravity based on a Lagrangian density made up of the Hilbert-Palatini term and, instead of the Holst term, the Nieh-Yan topological density. The resulting set of constraints in the time gauge are shown to lead to a theory in terms of a real SU (2) connection which is exactly the same as that of Barbero and Immirzi with the coefficient of the Nieh-Yan term identified as the inverse of Barbero-Immirzi parameter. This provides a topological interpretation for this parameter. Matter coupling can then be introduced in the usual manner, without changing the universal topological Nieh-Yan term.
Physical Review A, 1993
In this paper we show that (a) all the known exact solutions of the problem of Nanyons in oscilla... more In this paper we show that (a) all the known exact solutions of the problem of Nanyons in oscillator potential precisely arise from the collective degrees of freedom, (b) the system is pseudo-integrable ala Richens and Berry. We conclude that the exact solutions are trivial thermodynamically as well as dynamically.
arXiv (Cornell University), Apr 17, 2010
arXiv (Cornell University), Jul 5, 2022
These are lecture notes of the QFT-I course I gave in an online mode at Chennai Mathematical Inst... more These are lecture notes of the QFT-I course I gave in an online mode at Chennai Mathematical Institute. The course focussed on the free relativistic quantum fields, their interactions in the perturbative scattering framework, standard computations of QED processes, radiative corrections at 1-loop with renormalization and an introduction to the toolbox of path integrals.
General Relativity and Gravitation, 1997
Einstein equations with T µν = k µ k ν + ℓ µ ℓ ν where k, ℓ are null are considered with spherica... more Einstein equations with T µν = k µ k ν + ℓ µ ℓ ν where k, ℓ are null are considered with spherical symmetry and staticity. The solution has naked singularity and is not asymptotically flat. However, it may be interpreted as an envelope for any static spherical body making it more massive. Such an interpretation and some of its implications are detailed.
Since the past Iagrg meeting in December 2004, new developments in loop quantum cosmology have ta... more Since the past Iagrg meeting in December 2004, new developments in loop quantum cosmology have taken place, especially with regards to the resolution of the Big Bang singularity in the isotropic models. The singularity resolution issue has been discussed in terms of physical quantities (expectation values of Dirac observables) and there is also an ``improved'' quantization of the Hamiltonian constraint. These developments are briefly discussed. This is an expanded version of the review talk given at the 24$^{\mathrm{th}}$ IAGRG meeting in February 2007.
Fermions constitute an important component of matter and their quantization in presence of dynami... more Fermions constitute an important component of matter and their quantization in presence of dynamical gravity is essential for any theory of quantum gravity. We revisit the classical formulation adapted for a background free quantization. The analysis is carried out with the Hilbert-Palatini form for gravity together with the Nieh-Yan topological term which keeps the nature of Barbero-Immirzi parameter independent of inclusion of arbitrary matter with arbitrary couplings. With dynamical gravity, a priori, there are two distinct notions of `parity' - orientation reversing diffeomorphisms and improper Lorentz rotations. The invariance properties of the action and the canonical framework are different with respect to these and gravitational origin of parity violation seems ambiguous.
Pramana, 2004
This is a written, expanded version of the summary talk given at the conclusion of the ICGC-2004 ... more This is a written, expanded version of the summary talk given at the conclusion of the ICGC-2004 held at Cochin. Brief introductory remarks are included to provide a slightly wider context to the theme talks.
Physics Letters B, 1983
Abstract A general framework is developed to analyse the influence of soft partons on the high en... more Abstract A general framework is developed to analyse the influence of soft partons on the high energy behaviour of the Drell-Yan cross section.
Physical Review D, 2005
Loop quantization of diagonalized Bianchi class A models, leads to a partial difference equation ... more Loop quantization of diagonalized Bianchi class A models, leads to a partial difference equation as the Hamiltonian constraint at the quantum level. A criterion for testing a viable semiclassical limit has been formulated in terms of existence of the so-called pre-classical solutions. We demonstrate the existence of pre-classical solutions of the quantum equation for the vacuum Bianchi I model. All these solutions avoid the classical singularity at vanishing volume.
Physical Review D, 2005
In classical general relativity, the generic approach to the initial singularity is usually under... more In classical general relativity, the generic approach to the initial singularity is usually understood in terms of the BKL scenario. In this scenario, along with the Bianchi IX model, the exact, singular, Kasner solution of vacuum Bianchi I model also plays a pivotal role. Using an effective classical Hamiltonian obtained from loop quantization of vacuum Bianchi I model, exact solution is obtained which is non-singular due to a discreteness parameter. The solution is parameterized in exactly the same manner as the usual Kasner solution and reduces to the Kasner solution as discreteness parameter is taken to zero. At the effective Hamiltonian level, the avoidance of Kasner singularity uses a mechanism distinct from the 'inverse volume' modifications characteristic of loop quantum cosmology.
Physical Review D, 1983
An alternate and more general form of factorization for the Drell-Yan process is derived in pertu... more An alternate and more general form of factorization for the Drell-Yan process is derived in perturbation theory. Corresponding generalized anomalous dimensions are defined. Simple calculations verify Mueller's conjecture for the recovery of improved parton-model results at very high energies. The approach offers a general framework to analyze the role played by soft partons, and to study their influence on asymptotic behavior.
Modern Physics Letters A, 2002
This is a review talk describing the recent work of Martin Bojowald on Loop Quantum Cosmology.