Papers by Soumitra Sengupta
Physical Review D, 2007
Supersymmetry offers a cold dark matter candidate, provided that lepton number is not violated by... more Supersymmetry offers a cold dark matter candidate, provided that lepton number is not violated by an odd number of units. On the other hand, lepton number violation by even (two) units gives us an attractive mechanism of neutrino mass generation. Here we offer an explanation of this, in a supergravity framework underlying a supersymmetric scenario, the essential feature being particles carrying lepton numbers, which interact only gravitationally with all other known particles. It is shown that one can have the right amount of ∆L = 2 effect giving rise to neutrino masses, whereas the lifetime for ∆L = 1 decays of the lightest supersymmetric particle can be prolonged beyond the present age of the universe.
Physical Review D, 2012
In the Randall-Sundrum model, a bulk neutrino field in the 5-dimensional spacetime can give rise ... more In the Randall-Sundrum model, a bulk neutrino field in the 5-dimensional spacetime can give rise to tiny Dirac masses to neutrinos. In such a scenario, we have computed the contribution of the bulk neutrino field to the anomalous magnetic moment (g − 2) µ of muon. We have computed this contribution in the 't Hooft-Feynman gauge and have found that the contribution has the right sign to fit the current discrepancy between the experiment and the standard model value of (g − 2) µ. We have also studied possible constraints on the model parameters by including contributions to (g − 2) µ from other sources such as bulk gravitons.
Physical Review D, 2008
Recent PVLAS data put stringent constraints on the measurement of birefringence and dichroism of ... more Recent PVLAS data put stringent constraints on the measurement of birefringence and dichroism of electromagnetic waves travelling in a constant and homogeneous magnetic field. There have been theoretical predictions in favour of such phenomena when appropriate axion-electromagnetic coupling is assumed. Origin of such a coupling can be traced in a low energy string action from the requirement of quantum consistency. The resulting couplings in such models are an artifact of the compactification of the extra dimensions present inevitably in a string scenario. The moduli parameters which encode the compact manifold therefore play a crucial role in determining the axion-photon coupling. In this work we examine the possible bounds on the value of compact modulus that emerge from the experimental limits on the coupling obtained from the PVLAS data. In particular we focus into the Randall-Sundrum (RS) type of warped geometry model whose modulus parameter is already restricted from the requirement of the resolution of gauge hierarchy problem in connection with the mass of the Higgs. We explore the bound on the modulus for a wide range of the axion mass for both the birefringence and the dichroism data in PVLAS. We show that the proposed value of the modulus in the RS scenario can only be accommodated for axion mass > ∼ 0.3 eV.
EPL (Europhysics Letters), 2010
The Kaluza-Klein (KK)modes of a massive scalar field on a 3-brane embedded in six dimensional mul... more The Kaluza-Klein (KK)modes of a massive scalar field on a 3-brane embedded in six dimensional multiply warped spacetime are determined. Due to the presence of warping along both the extra dimensions the KK mass spectrum splits into two closely spaced branches which is a distinct feature of this model compared to the five dimensional Randall-Sundrum model. This new cluster of the KK mode spectrum is expected to have interesting phenomenological implications for the upcoming collider experiments. Such a scenario may also be extended for even larger number of orbifolded extra dimensions.
EPL (Europhysics Letters), 2009
We study the stabilization of inter-brane spacing modulus of generalized warped brane models with... more We study the stabilization of inter-brane spacing modulus of generalized warped brane models with a nonzero brane cosmological constant. Employing Goldberger-Wise stabilization prescription of brane world models with a bulk scalar field, we show that the stabilized value of the modulus generally depends on the value of the brane cosmological constant. Our result further reveals that the stabilized modulus value corresponding to a vanishingly small cosmological constant can only resolve the gauge hierarchy problem simultaneously. This in turn vindicates the original Randall-Sundrum model where the 3-brane cosmological constant was chosen to be zero.
The European Physical Journal C, 2005
In this work we explore the geodesic deviations of spinning test particles in a string inspired E... more In this work we explore the geodesic deviations of spinning test particles in a string inspired Einstein-Kalb Ramond background. Such a background is known to be equivalent to a spacetime geometry with torsion. We have shown here that the antisymmetric Kalb-Ramond field has significant effect on the geodesic deviation of a spinning test particle. A search for an observational evidence of such an effect in astrophysical experiments may lead to a better undestanding of the geometry of the background spacetime.
The European Physical Journal C - Particles and Fields, 2004
The possibility of parity violation in a gravitational theory with torsion is extensively explore... more The possibility of parity violation in a gravitational theory with torsion is extensively explored in four and higher dimensions. In the former case, we have listed our conclusions on when and whether parity ceases to be conserved, with both two-and three-index antisymmetry of the torsion field. In the latter, the bulk spacetime is assumed to have torsion, and the survival of parity-violating terms in the four dimensional effective action is studied, using the compactification schemes proposed by Arkani-Hamed-Dimopoulos-Dvali and Randall-Sundrum. An interesting conclusion is that the torsion-axion duality arising in a stringy scenario via the second rank antisymmetric Kalb-Ramond field leads to conservation of parity in the gravity sector in any dimension. However, parity-violating interactions do appear for spin 1/2 fermions in such theories, which can have crucial phenomenological implications.
Modern Physics Letters A, 2007
We investigate split supersymmetry (SUSY) within a supergravity framework, where local SUSY is br... more We investigate split supersymmetry (SUSY) within a supergravity framework, where local SUSY is broken by the F-term of a hidden sector chiral superfield X. With reasonably general assumptions, we show that the fermionic component of X will always have mass within a TeV. Though its coupling to the observable sector superfields is highly suppressed in TeV scale SUSY, we show that it can be enhanced by many orders in split SUSY, leading to its likely participation in accelerator phenomenology. We conclude with a specific example of such a scenario in a string based supergravity model.
Physical Review D, 2005
Rotation angle of the plane of polarization of the distant galactic radio waves has been estimate... more Rotation angle of the plane of polarization of the distant galactic radio waves has been estimated in a string inspired axion-dilaton background. It is found that the axion, dual to the field strength of the second rank massless antisymmetric Kalb-Ramond field in the string spectrum, ...
The European Physical …, Jan 1, 2002
Physical review letters, Jan 1, 2002
Classical and Quantum Gravity, Jan 1, 1999
Physical Review D, Jan 1, 2005
Arxiv preprint hep-th/0102073, Jan 1, 2001
Physical Review D, Jan 1, 2003
Physics Letters B, Jan 1, 2001
Physics Letters B, Jan 1, 1999
Physical Review D, Jan 1, 2002
Physical Review D, Jan 1, 2009
Physical Review D, Jan 1, 2004
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Papers by Soumitra Sengupta