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Amitabha Lahiri

Publications and source records attributed to Amitabha Lahiri.

At least 55 records · Page 3Linked to original sources
arXiv2016

Alignment, reverse alignment, and wrong sign Yukawa couplings in two Higgs doublet models

We consider two Higgs doublet models with a softly broken U(1) symmetry, for various limiting values of the scalar mixing angles $α$ and $β$. These correspond to the Standard Model Higgs particle being the lighter CP-even scalar (alignment) or the heavier CP-even scalar (reverse alignment), and also the limit in which some of the Yukawa couplings of this particle are of the opposite sign from the vector boson couplings (wrong sign). In these limits we impose a criterion for naturalness by demanding that quadratic divergences cancel at one loop. We plot the allowed masses of the remaining physical scalars based on naturalness, stability, perturbative unitarity and constraints coming from the $ρ$ parameter. We also calculate the $h\to γγ$ decay rate in the wrong sign limit.

hep-ph↗
arXiv2016

Quark ACM with topologically generated gluon mass

We investigate the effect of a small, gauge-invariant mass of the gluon on the anomalous chromomagnetic moment of quarks (ACM) by perturbative calculations at one loop level. The mass of the gluon is taken to have been generated via a topological mass generation mechanism, in which the gluon acquires a mass through its interaction with an antisymmetric tensor field $B_{μν}$. For a small gluon mass $(<10$ MeV), we calculate the ACM at momentum transfer $q^2=-M_Z^2$. We compare those with the ACM calculated for the gluon mass arising from a Proca mass term. We find that the ACM of up, down, strange and charm quarks vary significantly with the gluon mass, while the ACM of top and bottom quarks show negligible gluon mass dependence. The mechanism of gluon mass generation is most important for the strange quarks ACM, but not so much for the other quarks. We also show the results at $q^2=-m_t^2$. We find that the dependence on gluon mass at $q^2=-m_t^2$ is much less than at $q^2=-M_Z^2$ for all quarks.

hep-ph↗
arXiv2016

Construction of Categorical Bundles from Local Data

A categorical principal bundle is a structure comprised of categories that is analogous to a classical principal bundle; examples arise from geometric contexts involving bundles over path spaces. We show how a categorical principal bundle can be constructed from local data specified through transition functors and natural transformations.

math.CT↗
arXiv2015

Weak field limit in vierbein-Einstein-Palatini formalism and Fierz-Pauli Equation

We consider the weak field limit of gravity in the vierbein-Einstein-Palatini formalism, find the action and the equations for perturbations around an arbitrary background, and compare them with the usual metric perturbation equations. We also write the Fierz-Pauli equations for massive gravitons on an arbitrary curved background in this formalism.

gr-qc↗
arXiv2015

Twisted-Product Categorical Bundles

Categorical bundles provide a natural framework for gauge theories involving multiple gauge groups. Unlike the case of traditional bundles there are distinct notions of triviality, and hence also of local triviality, for categorical bundles. We study categorical principal bundles that are product bundles in the categorical sense, developing the relationship between functorial sections of such bundles and trivializations. We construct functorial cocycles with values in categorical groups using a suitable family of locally defined functions on the object space of the base category. Categorical product bundles being too rigid to give a widely applicable model for local triviality, we introduce the notion of a twisted-product categorical bundle. We relate such bundles to decorated categorical bundles that contain more information, specifically parallel transport data.

math.DG↗
arXiv2015

Dimensional reduction of four-dimensional topologically massive gauge theory

We study topologically massive (B \wedge F) Abelian and non-Abelian gauge theories in four dimensions, and reduce them to three dimensions by assuming that the fields do not propagate in one of the spatial directions. For certain gauge choices the reduced theories are the Jackiw-Pi models of massive gauge fields.

hep-th↗
arXiv2015

Masses of physical scalars in two Higgs doublet models

We find bounds on scalar masses resulting from a criterion of naturalness, in a broad class of two Higgs doublet models (2HDMs). Specifically, we assume the cancellation of quadratic divergences in what are called the type I, type II, lepton-specific and flipped 2HDMs, with an additional U(1) symmetry. This results in a set of relations among masses of the physical scalars and coupling constants, a generalization of the Veltman conditions of the Standard Model. Assuming that the lighter $CP$-even neutral Higgs particle is the observed scalar particle of mass $\sim$125 GeV, and imposing further the constraints from the electroweak T-parameter, stability, and perturbative unitarity, we calculate the range of the mass of each of the remaining physical scalars.

hep-ph↗
arXiv2015

4D Topological Mass by Gauging Spin

We propose a spin gauge field theory in which the curl of a Dirac fermion current density plays the role of the pseudovector charge density. In this field-theoretic model, spin interactions are mediated by a single scalar gauge boson in its antisymmetric tensor formulation. We show that these long range spin interactions induce a gauge invariant photon mass in the one-loop effective action. The fermion loop generates a coupling between photons and the spin gauge boson, which acquires thus charge. This coupling represents also an induced, gauge invariant, topological mass for the photons, leading to the Meissner effect. The one-loop effective equations of motion for the charged spin gauge boson are the London equations. We propose thus spin gauge interactions as an alternative, topological mechanism for superconductivity in which no spontaneous symmetry breaking is involved.

hep-th↗
arXiv2015

Connections on decorated path space bundles

For a principal bundle $P\to M$ equipped with a connection ${\bar A}$, we study an infinite dimensional bundle ${\mathcal P}^{\rm dec}_{\bar A}P$ over the space of paths on $M$, with the points of ${\mathcal P}^{\rm dec}_{\bar A}P$ being horizontal paths on $P$ decorated with elements of a second structure group. We construct parallel transport processes on such bundles and study holonomy bundles in this setting. We explain the relationship with categorical geometry and explore the notion of categorical connections on categorical principal bundles in a concrete differential geometric way.

math.DG↗
arXiv2014

Kaluza Ansatz applied to Eddington inspired Born-Infeld Gravity

We apply Kaluza's procedure to Eddington-inspired Born-Infeld action in gravity in five dimensions. The resulting action contains, in addition to the usual four-dimensional actions for gravity and electromagnetism, nonlinear couplings between the electromagnetic field strength and curvature. Considering the spherically symmetric solution as an example we find the lowest order corrections for the Reissner-Nordström metric and the electromagnetic field.

gr-qc↗
arXiv2014

Anomalous chromomagnetic moment of quarks

We do a perturbative calculation of the anomalous chromomagnetic dipole moment of quarks at one-loop, also considering the effect of a small gauge-invariant mass of the gluon. We find partial agreement with a previous calculation, as well as a divergence. We explain these results by noting that perturbation theory is not valid at the energy scales where these calculations were done, and proceed to give the results at the $M_Z$ scale. We find significant variation, of the anomalous moment of the light quarks, as a function of gluon mass.

hep-ph↗
arXiv2014

Twisted actions of categorical groups

We develop a theory of twisted actions of categorical groups using a notion of semidirect product of categories. We work through numerous examples to demonstrate the power of these notions. Turning to representations, which are actions that respect vector space structures, we establish an analog of Schur's lemma in this context. Keeping new terminology to a minumum, we concentrate on examples exploring the essential new notions introduced.

math.CT↗
arXiv2014

$β$-function for topologically massive gluons

We calculate the quantum corrections to the two-point function of four dimensional topologically massive non-Abelian vector fields at one loop order for $SU(N)$ gauge theory in Feynman-'t Hooft gauge. We calculate the beta function of the gauge coupling constant and find that the theory becomes asymptotically free faster than pure $SU(N)$ gauge theory.

hep-ph↗
arXiv2013

Mass function and particle creation in Schwarzschild-de Sitter spacetime

We construct a mass or energy function for the non-Nariai class Schwarzschild-de Sitter black hole spacetime in the region between the black hole and the cosmological event horizons. The mass function is local, positive definite, continuous and increases monotonically with the radial distance from the black hole event horizon. We derive the Smarr formula using this mass function, and demonstrate that the mass function reproduces the two-temperature Schwarzschild-de Sitter black hole thermodynamics, along with a term corresponding to the negative pressure due to positive cosmological constant. We further give a field theoretic derivation of the particle creation by both the horizons and discuss its connection with the mass function.

gr-qc↗
arXiv2012

Massive spin-2 and spin-1/2 no hair theorems for stationary axisymmetric black holes

We present a proof of the no hair theorems corresponding to free massive non-perturbative Pauli-Fierz spin-2 and perturbative massive spin-1/2 fields for stationary axisymmetric de Sitter black hole spacetimes of dimension four with two commuting Killing vector fields. The applicability of these results for asymptotically flat and anti-de Sitter spacetimes are also discussed.

gr-qc↗
arXiv2012

Path space connections and categorical geometry

We study a type of connection forms, given by Chen integrals, over pathspaces by placing such forms within a category-theoretic framework of principal bundles and connections. We introduce a notion of 'decorated' principal bundles, develop parallel transport on such bundles, and explore specific examples in the context of pathspaces.

math.CT↗
arXiv2012

A Morphism Double Category and Monoidal Structure

A double category is constructed from a `fattened' version of a given category, motivated in part by a context of parallel transport. We also study monoidal structures on the underlying category and on the fattened category.

math-ph↗