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Aashish Sandeep - One of the best experts on this subject based on the ideXlab platform.
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Gravitational waves from inflation with Antisymmetric Tensor field
2020Co-Authors: Aashish Sandeep, Padhy Abhilash, Panda SukantaAbstract:We build upon the past studies of inflation with rank-2 Antisymmetric Tensor field, including here the Tensor perturbations to metric. We perform a comprehensive analysis of the background dynamics of our model in the presence of non-minimal coupling curvature terms $R$ and $R_{\mu \nu}$. We find appropriate conditions on the nonminimal coupling parameters to satisfy the constraint of speed of propagation of gravitational waves. Including the Tensor perturbations, the model is found to be free from ghost instabilities with minimal constraints on the parameters. We also study the evolution of gravitational waves, calculate the power spectrum and the Tensor spectral index.Comment: 19 pages, 3 figures, 1 tabl
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Gravitational waves from inflation with Antisymmetric Tensor field
'IOP Publishing', 2020Co-Authors: Aashish Sandeep, Padhy Abhilash, Panda SukantaAbstract:We build upon the past studies of inflation with rank-2 Antisymmetric Tensor field, including here the Tensor perturbations to metric. We perform a comprehensive analysis of the background dynamics of our model in the presence of non-minimal coupling curvature terms $R$ and $R_{\mu \nu}$. We find appropriate conditions on the nonminimal coupling parameters to satisfy the constraint of speed of propagation of gravitational waves. Including the Tensor perturbations, the model is found to be free from ghost instabilities with minimal constraints on the parameters. We also study the evolution of gravitational waves, calculate the power spectrum and the Tensor spectral index.Comment: A calculational error has been corrected leading to minor changes in results without affecting conclusions; matches published version 21 pages, 3 figures, 1 tabl
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Covariant Quantum Gravitational Corrections to Scalar and Tensor Field Models
2020Co-Authors: Aashish SandeepAbstract:Recent and upcoming experimental data as well as the possibility of rich phenomenology have spiked interest in studying the quantum effects in cosmology at low (inflation-era) energy scales. One of the approaches to find covariant quantum corrections is the DeWitt-Vilkovisky's (DV) covariant effective action formalism that is gauge invariant and background field invariant. We use the DeWitt-Vilkovisky method to study formal and cosmological aspects of quantum fields in curved spacetime, and take initial steps towards studying quantum gravitational corrections in cosmological setting. The thesis comprises of mainly two parts. We first study the formal aspects of rank-2 Antisymmetric Tensor field which appear in the low energy limit of superstring models and are thus relevant in the early universe, in particular the quantization and quantum equivalence properties, for the case with and without spontaneous Lorentz violation. The effective action is generalized for gauge theories whose gauge parameters possess additional symmetries. When used in the case of spontaneously Lorentz violating Antisymmetric Tensor field model, it is found that classical equivalence with a vector theory breaks down at one-loop level due to the presence of Lorentz violating terms. The final chapter of this thesis is devoted to taking first steps towards exploring applications of DV method in early universe cosmology. We calculate perturbatively the covariant one-loop quantum gravitational effective action for a scalar field model inspired by the recently proposed nonminimal natural inflation model. The effective potential is evaluated taking into account the finite corrections, and an order-of-magnitude estimate of the one-loop corrections reveals that gravitational and non-gravitational corrections have same or comparable magnitudes.Comment: 130 pages, 2 figures; PhD thesis (Indian Institute of Science Education and Research Bhopal, April 2020) based on previously published works in arxiv:1803.10157, arxiv:1806.08194, arxiv:1903.11364, arxiv:1905.12249 and arxiv:2001.0735
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On the quantum equivalence of an Antisymmetric Tensor field with spontaneous Lorentz violation
'World Scientific Pub Co Pte Lt', 2020Co-Authors: Aashish Sandeep, Panda SukantaAbstract:We present an explicit proof that a minimal model of rank-2 Antisymmetric field with spontaneous Lorentz violation and a classically equivalent vector field model are also quantum equivalent, by calculating quantum effective actions of both theories. We comment on the issues encountered while checking quantum equivalence in curved spacetime.Comment: published versio
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Note on stability and microcausality in Lorentz violating Antisymmetric Tensor field
2020Co-Authors: Aashish SandeepAbstract:The fundamental issues of microcausality and energy positivity conditions are important to be investigated in the context of spontaneous Lorentz violating theories. We check the microcausality and energy positivity conditions for a free rank-2 Antisymmetric Tensor field with spontaneous Lorentz violating term and a classically equivalent vector theory from dispersion relations and propagators, and find that the two theories lead to different conditions. While the Antisymmetric Tensor theory satisfies energy positivity condition and can satisfy microcausality condition for a particular choice of vacuum value, the vector theory violates both energy positivity and microcausality conditions.Comment: 12 page
Panda Sukanta - One of the best experts on this subject based on the ideXlab platform.
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Gravitational waves from inflation with Antisymmetric Tensor field
2020Co-Authors: Aashish Sandeep, Padhy Abhilash, Panda SukantaAbstract:We build upon the past studies of inflation with rank-2 Antisymmetric Tensor field, including here the Tensor perturbations to metric. We perform a comprehensive analysis of the background dynamics of our model in the presence of non-minimal coupling curvature terms $R$ and $R_{\mu \nu}$. We find appropriate conditions on the nonminimal coupling parameters to satisfy the constraint of speed of propagation of gravitational waves. Including the Tensor perturbations, the model is found to be free from ghost instabilities with minimal constraints on the parameters. We also study the evolution of gravitational waves, calculate the power spectrum and the Tensor spectral index.Comment: 19 pages, 3 figures, 1 tabl
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Gravitational waves from inflation with Antisymmetric Tensor field
'IOP Publishing', 2020Co-Authors: Aashish Sandeep, Padhy Abhilash, Panda SukantaAbstract:We build upon the past studies of inflation with rank-2 Antisymmetric Tensor field, including here the Tensor perturbations to metric. We perform a comprehensive analysis of the background dynamics of our model in the presence of non-minimal coupling curvature terms $R$ and $R_{\mu \nu}$. We find appropriate conditions on the nonminimal coupling parameters to satisfy the constraint of speed of propagation of gravitational waves. Including the Tensor perturbations, the model is found to be free from ghost instabilities with minimal constraints on the parameters. We also study the evolution of gravitational waves, calculate the power spectrum and the Tensor spectral index.Comment: A calculational error has been corrected leading to minor changes in results without affecting conclusions; matches published version 21 pages, 3 figures, 1 tabl
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On the quantum equivalence of an Antisymmetric Tensor field with spontaneous Lorentz violation
'World Scientific Pub Co Pte Lt', 2020Co-Authors: Aashish Sandeep, Panda SukantaAbstract:We present an explicit proof that a minimal model of rank-2 Antisymmetric field with spontaneous Lorentz violation and a classically equivalent vector field model are also quantum equivalent, by calculating quantum effective actions of both theories. We comment on the issues encountered while checking quantum equivalence in curved spacetime.Comment: published versio
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Avoiding instabilities in Antisymmetric Tensor field driven inflation
'Springer Science and Business Media LLC', 2019Co-Authors: Aashish Sandeep, Padhy Abhilash, Panda SukantaAbstract:Models of inflation with Antisymmetric Tensor studied in the past are plagued with ghost instability even in an unperturbed FRW background. We show that it is possible to avoid ghosts in an unperturbed FRW background by considering the most general kinetic term for Antisymmetric Tensor field. The kinetic part acquires a new gauge symmetry violating term whose effect on perturbed modes is to prevent the appearance of nondynamical modes, and thus avoid ghosts. For completeness, we perform a check for gradient instability and derive the conditions for perturbations to be free of gradient instability.Comment: 14 pages; Sec. III rewritten, with new and improved calculations for gradient stability analysis; matches published versio
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Quantum aspects of Antisymmetric Tensor field with spontaneous Lorentz violation
'American Physical Society (APS)', 2019Co-Authors: Aashish Sandeep, Panda SukantaAbstract:We study the quantization of a simple model of Antisymmetric Tensor field with spontaneous Lorentz violation in curved spacetime. We evaluate the 1-loop corrections at first order of metric perturbation, using a general covariant effective action approach. We revisit the issue of quantum equivalence, and find that it holds for non-Lorentz-violating modes but breaks down for Lorentz violating modes.Comment: 20 pages; minor corrections, text improvements, references added; published versio
D V Vassilevich - One of the best experts on this subject based on the ideXlab platform.
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zeta function for the laplace operator acting on forms in a ball with gauge boundary conditions
Communications in Mathematical Physics, 1997Co-Authors: E Elizalde, M Lygren, D V VassilevichAbstract:The Laplace operator acting on Antisymmetric Tensor fields in a D-dimensional Euclidean ball is studied. Gauge-invariant local boundary conditions (absolute and relative ones, in the language of Gilkey) are considered. The eigenfuctions of the operator are found explicitly for all values of D. Using in a row a number of basic techniques, as Mellin transforms, deformation and shifting of the complex integration contour and pole compensation, the zeta function of the operator is obtained. From its expression, in particular, ζ(0) and ζ'(0) are evaluated exactly. A table is given in the paper for D=3,4,...,8. The functional determinants and Casimir energies are obtained for D=3,4,...,6.
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zeta function for the laplace operator acting on forms in a ball with gauge boundary conditions
arXiv: High Energy Physics - Theory, 1996Co-Authors: E Elizalde, M Lygren, D V VassilevichAbstract:The Laplace operator acting on Antisymmetric Tensor fields in a $D$--dimensional Euclidean ball is studied. Gauge-invariant local boundary conditions (absolute and relative ones, in the language of Gilkey) are considered. The eigenfuctions of the operator are found explicitly for all values of $D$. Using in a row a number of basic techniques, as Mellin transforms, deformation and shifting of the complex integration contour, and pole compensation, the zeta function of the operator is obtained. From its expression, in particular, $\zeta (0)$ and $\zeta'(0)$ are evaluated exactly. A table is given in the paper for $D=3, 4, ...,8$. The functional determinants and Casimir energies are obtained for $D=3, 4, ...,6$.
Jorge Portoles - One of the best experts on this subject based on the ideXlab platform.
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odd intrinsic parity processes within the resonance effective theory of qcd
Journal of High Energy Physics, 2003Co-Authors: P Ruizfemenia, Antonio Pich, Jorge PortolesAbstract:We analyse the most general odd-intrinsic-parity effective lagrangian of QCD valid for processes involving one pseudoscalar with vector mesons described in terms of Antisymmetric Tensor fields. Substantial information on the odd-intrinsic-parity couplings is obtained by constructing the vector-vector-pseudoscalar Green's three-point function, at leading order in 1/NC, and demanding that its short-distance behaviour matches the corresponding OPE result. The QCD constraints thus enforced allow us to predict the decay amplitudes ω→πγ and ρ→πγ, and the (p6) corrections to π→γγ. Noteworthy consequences concerning the vector meson dominance assumption in the decay ω→3π are also extracted from the previous analysis.
Runqiu Yang - One of the best experts on this subject based on the ideXlab platform.
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Antisymmetric Tensor field and spontaneous magnetization in holographic duality
Physical Review D, 2015Co-Authors: Ronggen Cai, Runqiu YangAbstract:A real anti-symmetric Tensor field was introduced to realize a holographic magnetic ordered phase in our previous works. However, a more careful analysis shows there is a vector ghost in the model. In this paper we present a modified Lagrangian density for the anti-symmetric Tensor, which is ghost free and causality is well-defined, and keeps all the significant results in the original model qualitatively. We show this modified Lagrangian density could come from the dimensional compactification of $p$-form field in String/M-theory. For static curved space-time, we also prove that this modified model is ghost free and dose not violate causality. This new model offers a solid foundation for the application of Antisymmetric Tensor field in holographic duality, especially for the spontaneous magnetization.
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paramagnetism ferromagnetism phase transition in a dyonic black hole
Physical Review D, 2014Co-Authors: Runqiu YangAbstract:Coupling an Antisymmetric Tensor field to the electromagnetic field in a dyonic Reissner-Nordstrom-anti-de Sitter black hole background, we build a holographic model for the paramagnetism/ferromagnetism phase transition. In the case of zero magnetic field, the time reversal symmetry is broken spontaneously and spontaneous magnetization happens at low temperatures. The critical exponents are in agreement with the ones from mean field theory. In the case of nonzero magnetic field, the model realizes the hysteresis loop of a single magnetic domain and the magnetic susceptibility satisfies the Curie-Weiss law.