Soumitra SenGupta
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Soumitra SenGupta has a total of 91 co-authors. Here are the top co-authors by number of shared publications:
- Sumanta Chakraborty
Indian Association for the Cultivation of Science
48 shared publications - Indrani Banerjee
Department of Physics and Astronomy, National Institute of Technology, Rourkela, Odisha-769008, India
32 shared publications - Tanmoy Paul
Department of Physics, Visva-Bharati University, Santiniketan 731235, India
22 shared publications - Sayantan Choudhury
Centre For Cosmology and Science Popularization (CCSP) SGT University Haryana-122505 Gurugram Delhi-NCR India
9 shared publications - Bhaswati Mandal
School of Physical Sciences, Indian Association for the Cultivation of Science, Kolkata-700032, India
8 shared publications - Biswarup Mukhopadhyaya
Harish Chandra Research Institute
8 shared publications
Latest Publications
- Open Access
- 9 November 2026
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2026 (11)
Kaluza-Klein gravitons in a higher curvature warped geometry: a new perspective
A bstract: Kaluza-Klein (KK) Gravitons are the direct collider imprints of the higher dimensional bulk physics in our four dimensional universe, arising from the compactification of an extra spatial dimension. In this work, we consider a two-brane warped geometry with a 5D $$ f\left(\mathcal{R}\right)=\mathcal{R}+{\alpha \mathcal{R}}^2 $$ gravity along with a cosmological constant Λ. The warped spacetime provides an elegant resolution of the gauge-hierarchy problem without introducing any intermediate scale, while the Planck-scale curvature of the underlying AdS 5 bulk naturally motivates the inclusion of higher-curvature corrections. For small values of the higher-curvature parameter ( α ), we obtain the leading-order back-reacted warp factors perturbatively from the modified gravitational field equations. In the backdrop of a warped braneworld model, we have solved the Schrödinger-like equation governing the graviton fluctuations using a Euclidean path integral formalism, yielding the KK graviton spectrum and normalized wavefunctions directly from the corresponding quantum-mechanical propagator. Treating these results as the unperturbed background, we analytically determine the higher curvature corrections to the KK graviton spectrum and their couplings to Standard Model (SM) matter fields. We find that there is an appreciable upward shift in the KK graviton masses while leaving the graviton-SM couplings only mildly modified as compared to a model with only Einstein gravity in the bulk. However the net cross-section of processes involving virtual gravitons appears to be suppressed whereas the dilepton and diphoton decay widths of the gravitons are significantly enhanced because of the higher curvature corrections. Overall, these effects lead to observable modifications to both the production and decay signatures of massive KK gravitons and may be probed in some future precision collider experiments.- 9 November 2026
- Published by Springer Nature in Journal of High Energy Physics
- Vol. 2026 (11)
Open AccessKaluza-Klein gravitons in a higher curvature warped geometry: a new perspective
A bstract: Kaluza-Klein (KK) Gravitons are the direct collider imprints of the higher dimensional bulk physics in our four dimensional universe, arising from the compactification of an extra spatial dimension. In this work, we consider a two-brane warped geometry with a 5D $$ f\left(\mathcal{R}\right)=\mathcal{R}+{\alpha \mathcal{R}}^2 $$ gravity along with a cosmological constant Λ. The warped spacetime provides an elegant resolution of the gauge-hierarchy problem without introducing any intermediate scale, while the Planck-scale curvature of the underlying AdS 5 bulk naturally motivates the inclusion of higher-curvature corrections. For small values of the higher-curvature parameter ( α ), we obtain the leading-order back-reacted warp factors perturbatively from the modified gravitational field equations. In the backdrop of a warped braneworld model, we have solved the Schrödinger-like equation governing the graviton fluctuations using a Euclidean path integral formalism, yielding the KK graviton spectrum and normalized wavefunctions directly from the corresponding quantum-mechanical propagator. Treating these results as the unperturbed background, we analytically determine the higher curvature corrections to the KK graviton spectrum and their couplings to Standard Model (SM) matter fields. We find that there is an appreciable upward shift in the KK graviton masses while leaving the graviton-SM couplings only mildly modified as compared to a model with only Einstein gravity in the bulk. However the net cross-section of processes involving virtual gravitons appears to be suppressed whereas the dilepton and diphoton decay widths of the gravitons are significantly enhanced because of the higher curvature corrections. Overall, these effects lead to observable modifications to both the production and decay signatures of massive KK gravitons and may be probed in some future precision collider experiments. - Open Access
- 15 September 2026
- Published by American Physical Society (APS) in APS Open Science
- Vol. 1, 000133
Tachyonic instability in Randall-Sundrum braneworld scenarios
Low-energy effective theories provide a natural description of four-dimensional physics in higher-dimensional geometries, where the imprint of the bulk geometry appears as parameters of the lower-dimensional theory. Inspired by the Damour-Esposito-Farése model of spontaneous scalarization in first-generation scalar-tensor theories of gravity, we investigate the possibility of tachyonic instability and spontaneous scalarization in braneworld scenarios. We consider the two-brane Randall-Sundrum (RS) model where the low-energy effective theory on either brane is of scalar-tensor nature with the extra-dimensional radion playing the role of the scalar. We have determined the possibilities for tachyonic (in)stability of the radion field on either brane in three scenarios: the RS model with fine-tuning conditions in which the potential of the radion field vanishes identically, the RS model without fine-tunings where the radion potential arises purely from the gravity sector, and the RS model with a bulk stabilizing field that generates a radion potential with a minimum. With the bulk stabilizing field, we have found that on-brane matter with T > 0 changes the vacuum expectation value (VEV) of the radion, destroying the resolution of the gauge hierarchy problem, whereas on-brane matter with T < 0 does not alter the stability and VEV of the radion. We further determined the exact condition of tachyonic (in)stability of radion field with the on-brane dS 4 and AdS 4 geometries.
- 15 September 2026
- Published by American Physical Society (APS) in APS Open Science
- Vol. 1, 000133
Open AccessTachyonic instability in Randall-Sundrum braneworld scenarios
Low-energy effective theories provide a natural description of four-dimensional physics in higher-dimensional geometries, where the imprint of the bulk geometry appears as parameters of the lower-dimensional theory. Inspired by the Damour-Esposito-Farése model of spontaneous scalarization in first-generation scalar-tensor theories of gravity, we investigate the possibility of tachyonic instability and spontaneous scalarization in braneworld scenarios. We consider the two-brane Randall-Sundrum (RS) model where the low-energy effective theory on either brane is of scalar-tensor nature with the extra-dimensional radion playing the role of the scalar. We have determined the possibilities for tachyonic (in)stability of the radion field on either brane in three scenarios: the RS model with fine-tuning conditions in which the potential of the radion field vanishes identically, the RS model without fine-tunings where the radion potential arises purely from the gravity sector, and the RS model with a bulk stabilizing field that generates a radion potential with a minimum. With the bulk stabilizing field, we have found that on-brane matter with T > 0 changes the vacuum expectation value (VEV) of the radion, destroying the resolution of the gauge hierarchy problem, whereas on-brane matter with T < 0 does not alter the stability and VEV of the radion. We further determined the exact condition of tachyonic (in)stability of radion field with the on-brane dS 4 and AdS 4 geometries.
- 1 September 2026
- Published by IOP Publishing in Journal of Cosmology and Astroparticle Physics
- Vol. 2026 (09)
Inflationary torsion as a source of gravitational waves: observational limits and viability
We investigate the stochastic gravitational wave background (SGWB) generated at second order by spacetime torsion during an epoch of canonical single-field slow-roll inflation. The torsional degrees of freedom are modeled via an effective rank-2 antisymmetric Kalb-Ramond (KR) field, assumed to remain energetically subdominant throughout inflation. We find that the KR-induced second-order SGWB is tightly constrained by current indirect bounds from CMB observations (Planck 2018 and BICEP/Keck 2015), requiring an exceptionally low inflationary Hubble scale, H ≲ 10 -42.6 M Pl . However, such an ultra-low inflationary scale is incompatible with the standard thermal history of the Universe. In particular, the requirement of successful Big Bang Nucleosynthesis (BBN), T BBN ∼ 𝒪(1) MeV, implies a lower bound H ≳ 10 -41.0 M Pl even under the most optimistic assumption of instantaneous reheating, with raised lower bounds arising for non-standard post-inflationary evolution. This tension precludes a consistent cosmological scenario in which torsion is dynamically relevant during inflation while remaining compatible with both current observational constraints and standard early-Universe evolution. We therefore conclude that the torsional sector must be effectively absent during inflation, allowing cosmological gravitational wave observations to place stringent constraints on, and potentially rule out, torsion in the very early Universe.
- 1 September 2026
- Published by IOP Publishing in Journal of Cosmology and Astroparticle Physics
- Vol. 2026 (09)
Inflationary torsion as a source of gravitational waves: observational limits and viability
We investigate the stochastic gravitational wave background (SGWB) generated at second order by spacetime torsion during an epoch of canonical single-field slow-roll inflation. The torsional degrees of freedom are modeled via an effective rank-2 antisymmetric Kalb-Ramond (KR) field, assumed to remain energetically subdominant throughout inflation. We find that the KR-induced second-order SGWB is tightly constrained by current indirect bounds from CMB observations (Planck 2018 and BICEP/Keck 2015), requiring an exceptionally low inflationary Hubble scale, H ≲ 10 -42.6 M Pl . However, such an ultra-low inflationary scale is incompatible with the standard thermal history of the Universe. In particular, the requirement of successful Big Bang Nucleosynthesis (BBN), T BBN ∼ 𝒪(1) MeV, implies a lower bound H ≳ 10 -41.0 M Pl even under the most optimistic assumption of instantaneous reheating, with raised lower bounds arising for non-standard post-inflationary evolution. This tension precludes a consistent cosmological scenario in which torsion is dynamically relevant during inflation while remaining compatible with both current observational constraints and standard early-Universe evolution. We therefore conclude that the torsional sector must be effectively absent during inflation, allowing cosmological gravitational wave observations to place stringent constraints on, and potentially rule out, torsion in the very early Universe.
- Open Access
Modified Gravity as Entropic Cosmology
The present work reveals a direct correspondence between modified theories of gravity (cosmology) and entropic cosmology based on the thermodynamics of apparent horizon. It turns out that due to the total differentiable property of entropy, the usual thermodynamic law (used for Einstein gravity) needs to be generalized for modified gravity theories having more than one thermodynamic degree of freedom (d.o.f.). For the modified theories having n number of thermodynamic d.o.f., the corresponding horizon entropy is given by terms containing the time derivatives of up to -th order, and moreover, the coefficient(s) of the derivative term(s) are proportional to the modification parameter of the gravity theory (compared to the Einstein gravity; is the Bekenstein–Hawking entropy). By identifying the independent thermodynamic variables from the first law of thermodynamics, we show that the equivalent thermodynamic description of modified gravity naturally allows the time derivative of the Bekenstein–Hawking entropy in the horizon entropy.Open AccessModified Gravity as Entropic Cosmology
The present work reveals a direct correspondence between modified theories of gravity (cosmology) and entropic cosmology based on the thermodynamics of apparent horizon. It turns out that due to the total differentiable property of entropy, the usual thermodynamic law (used for Einstein gravity) needs to be generalized for modified gravity theories having more than one thermodynamic degree of freedom (d.o.f.). For the modified theories having n number of thermodynamic d.o.f., the corresponding horizon entropy is given by terms containing the time derivatives of up to -th order, and moreover, the coefficient(s) of the derivative term(s) are proportional to the modification parameter of the gravity theory (compared to the Einstein gravity; is the Bekenstein–Hawking entropy). By identifying the independent thermodynamic variables from the first law of thermodynamics, we show that the equivalent thermodynamic description of modified gravity naturally allows the time derivative of the Bekenstein–Hawking entropy in the horizon entropy. - Open Access
- 9 March 2026
- Published by American Physical Society (APS) in Physical Review D
- Vol. 113 (6)
Thermal description of braneworld effective theories
Low-energy effective theories provide the natural description of four-dimensional physics in higher-dimensional geometries, where the imprint of the bulk appears as parameters of the lower-dimensional theory. Motivated by the recent progress in the first-order thermodynamic formulation of modified gravity theories, we investigate the thermodynamics of effective theories in braneworld scenarios and thereby the attractor mechanism toward general relativity in such theories. We consider the 2-brane Randall-Sundrum model, where the low-energy theory on either brane is of scalar-tensor nature with the extradimensional radion playing the role of the scalar. We study the thermodynamic implications of a nonvanishing gravitational contribution to the radion potential, and further explore the dynamics in the presence of a bulk stabilizing field.
- 9 March 2026
- Published by American Physical Society (APS) in Physical Review D
- Vol. 113 (6)
Open AccessThermal description of braneworld effective theories
Low-energy effective theories provide the natural description of four-dimensional physics in higher-dimensional geometries, where the imprint of the bulk appears as parameters of the lower-dimensional theory. Motivated by the recent progress in the first-order thermodynamic formulation of modified gravity theories, we investigate the thermodynamics of effective theories in braneworld scenarios and thereby the attractor mechanism toward general relativity in such theories. We consider the 2-brane Randall-Sundrum model, where the low-energy theory on either brane is of scalar-tensor nature with the extradimensional radion playing the role of the scalar. We study the thermodynamic implications of a nonvanishing gravitational contribution to the radion potential, and further explore the dynamics in the presence of a bulk stabilizing field.
- Open Access
On the Emergence of Einstein's Gravity from f(R) Gravity through Cosmological Evolution
$f(R)$-Gravity, a simple generalization of Einstein's General theory of Relativity has been considered in the context of Cosmology as one of the approaches to explain phenomena such as early-time inflation and late-time accelerated expansion of the Universe purely from the Gravity sector. In this work, we have considered a class of $f(R)$-Gravity theories with $f(R)=R+αR^n$ and it's dual scalar tensor theory in the Einstein frame. We have shown that in an isotropic and homogeneous background, for both positive and negative integral values of $n$, the extra scalar degree of freedom of the $f(R)$-theory (manifested as the scalar field in the Einstein frame action) dynamically freezes out due to cosmological evolution, resulting in the survival of only the Einstein-Hilbert term and a cosmological constant at most. This implies that all gravity models given as $R + αR^n$ inevitably evolve into pure Einstein gravity with a cosmological constant term through cosmological evolution.Open AccessOn the Emergence of Einstein's Gravity from f(R) Gravity through Cosmological Evolution
$f(R)$-Gravity, a simple generalization of Einstein's General theory of Relativity has been considered in the context of Cosmology as one of the approaches to explain phenomena such as early-time inflation and late-time accelerated expansion of the Universe purely from the Gravity sector. In this work, we have considered a class of $f(R)$-Gravity theories with $f(R)=R+αR^n$ and it's dual scalar tensor theory in the Einstein frame. We have shown that in an isotropic and homogeneous background, for both positive and negative integral values of $n$, the extra scalar degree of freedom of the $f(R)$-theory (manifested as the scalar field in the Einstein frame action) dynamically freezes out due to cosmological evolution, resulting in the survival of only the Einstein-Hilbert term and a cosmological constant at most. This implies that all gravity models given as $R + αR^n$ inevitably evolve into pure Einstein gravity with a cosmological constant term through cosmological evolution. - Open Access
- 16 December 2025
- Published by Springer Nature in The European Physical Journal C
- Vol. 85 (12) , 1430
Analyzing the general conditions for modulus stabilization in a warped braneworld
In braneworld scenarios with compact extra dimensions, the modulus field typically remains undetermined without an appropriate stabilization mechanism. A common approach introduces a bulk scalar field that generates an effective potential for the modulus with a stable minimum. In this work, we explore some novel aspects of such stabilization mechanisms. We study how the bulk scalar profile influences the stabilization procedure. Following the approach of Chacko et al. (JHEP 09, 121, 2013), we analyze several representative cases using methods of singular perturbation theory. We identify a consistent relationship between the structure of the bulk potential and the emergence of a stabilized modulus, and outline the general conditions that any bulk potential must satisfy to enable stabilization. In this context, we also examine a potential connection between geometric consistency conditions – specifically, the “brane world sum rules” – and the stabilized value of the modulus. In some scenarios where stabilization occurs, we find that these sum rules can offer additional constraints on the modulus, providing a complementary perspective on its determination. Taken together, these results offer a broader perspective on the mechanisms that govern modulus stabilization in higher-dimensional warped geometries.
- 16 December 2025
- Published by Springer Nature in The European Physical Journal C
- Vol. 85 (12) , 1430
Open AccessAnalyzing the general conditions for modulus stabilization in a warped braneworld
In braneworld scenarios with compact extra dimensions, the modulus field typically remains undetermined without an appropriate stabilization mechanism. A common approach introduces a bulk scalar field that generates an effective potential for the modulus with a stable minimum. In this work, we explore some novel aspects of such stabilization mechanisms. We study how the bulk scalar profile influences the stabilization procedure. Following the approach of Chacko et al. (JHEP 09, 121, 2013), we analyze several representative cases using methods of singular perturbation theory. We identify a consistent relationship between the structure of the bulk potential and the emergence of a stabilized modulus, and outline the general conditions that any bulk potential must satisfy to enable stabilization. In this context, we also examine a potential connection between geometric consistency conditions – specifically, the “brane world sum rules” – and the stabilized value of the modulus. In some scenarios where stabilization occurs, we find that these sum rules can offer additional constraints on the modulus, providing a complementary perspective on its determination. Taken together, these results offer a broader perspective on the mechanisms that govern modulus stabilization in higher-dimensional warped geometries.
- Open Access
- 13 December 2025
- Published by Springer Nature in The European Physical Journal C
- Vol. 85 (12)
Bouncing cosmologies in modified gravity with spacetime torsion
We explore the possibility of realizing a non-singular bounce in the early universe within the framework of modified gravity with spacetime torsion. In Einstein Cartan theory, torsion is embedded in the spacetime by adding an antisymmetric part in affine connection. We consider generalized version of the framework as $$f(\bar{R})$$ , $$\bar{R}$$ being the scalar of the modified curvature tensor. $$f(\bar{R})$$ gravity is recast in Einstein frame as non-minimally coupled scalar tensor theory where the scalar field gets coupled with a rank 2 antisymmetric torsion field through derivative couplings. We investigate whether the introduction of three additional torsion-dependent terms in Einstein frame help to realize a bounce. We first explore this cosmological system in the background of a homogeneous and isotropic FRW spacetime but inclusion of the torsion terms are insufficient to produce a bounce in this symmetric setting. Motivated by this limitation, we relax the symmetry and generalize the background to include inhomogeneity and anisotropy. In this setup, the dynamics is modified in such a way that a bouncing solution is possible without invoking phantom fields or energy condition violations. We have found the exact solutions of all the fields and reconstructed the modified gravity form. We have addressed the behaviour of the fields under perturbation and investigated the stability of the solutions. Constraints on the model parameters have also been derived based on cosmological observations.- 13 December 2025
- Published by Springer Nature in The European Physical Journal C
- Vol. 85 (12)
Open AccessBouncing cosmologies in modified gravity with spacetime torsion
We explore the possibility of realizing a non-singular bounce in the early universe within the framework of modified gravity with spacetime torsion. In Einstein Cartan theory, torsion is embedded in the spacetime by adding an antisymmetric part in affine connection. We consider generalized version of the framework as $$f(\bar{R})$$ , $$\bar{R}$$ being the scalar of the modified curvature tensor. $$f(\bar{R})$$ gravity is recast in Einstein frame as non-minimally coupled scalar tensor theory where the scalar field gets coupled with a rank 2 antisymmetric torsion field through derivative couplings. We investigate whether the introduction of three additional torsion-dependent terms in Einstein frame help to realize a bounce. We first explore this cosmological system in the background of a homogeneous and isotropic FRW spacetime but inclusion of the torsion terms are insufficient to produce a bounce in this symmetric setting. Motivated by this limitation, we relax the symmetry and generalize the background to include inhomogeneity and anisotropy. In this setup, the dynamics is modified in such a way that a bouncing solution is possible without invoking phantom fields or energy condition violations. We have found the exact solutions of all the fields and reconstructed the modified gravity form. We have addressed the behaviour of the fields under perturbation and investigated the stability of the solutions. Constraints on the model parameters have also been derived based on cosmological observations. - 20 May 2025
- Published by Springer Nature in The European Physical Journal Plus
- Vol. 140 (5) , 1-8
Constant curvature 3-branes in 5-D f(R) bulk
- 20 May 2025
- Published by Springer Nature in The European Physical Journal Plus
- Vol. 140 (5) , 1-8
Constant curvature 3-branes in 5-D f(R) bulk
- Open Access
Can spacetime torsion source an extremely red-tilted cosmological GW background?
In the presence of spacetime torsion, any generic $f(R)$ model of gravity is conformally dual to a scalar-tensor theory augmented with a second rank antisymmetric massless degree of freedom. We investigate the stochastic gravitational wave background (SGWB) that may be sourced directly at the second order by such a torsional field, treated perturbatively during an epoch of canonical, single-field, slow-roll inflation. The resulting second-order induced SGWB, which dominates over the primary inflationary GW background at all scales, peaks only at ultra-low frequencies, and is found to be extremely red-tilted with an effective tensor spectral index $α_{\rm T}\sim-6$ on matter-dominated scales. The signal is potentially within the reach of upcoming indirect GW probes on very large scales $k\lesssim10^{-2}\:\textrm{Mpc}^{-1}$, i.e., next-generation CMB experiments like the LiteBIRD. In the near future, observation of such a markedly red-tilted SGWB on CMB scales could hence provide a novel and unique clue in favour of torsional gravity during the inflationary era.Open AccessCan spacetime torsion source an extremely red-tilted cosmological GW background?
In the presence of spacetime torsion, any generic $f(R)$ model of gravity is conformally dual to a scalar-tensor theory augmented with a second rank antisymmetric massless degree of freedom. We investigate the stochastic gravitational wave background (SGWB) that may be sourced directly at the second order by such a torsional field, treated perturbatively during an epoch of canonical, single-field, slow-roll inflation. The resulting second-order induced SGWB, which dominates over the primary inflationary GW background at all scales, peaks only at ultra-low frequencies, and is found to be extremely red-tilted with an effective tensor spectral index $α_{\rm T}\sim-6$ on matter-dominated scales. The signal is potentially within the reach of upcoming indirect GW probes on very large scales $k\lesssim10^{-2}\:\textrm{Mpc}^{-1}$, i.e., next-generation CMB experiments like the LiteBIRD. In the near future, observation of such a markedly red-tilted SGWB on CMB scales could hence provide a novel and unique clue in favour of torsional gravity during the inflationary era.