24 citations · 153 across the 16 of their papers we have counts for
17 papers
The Basilica group of the Grigorchuk-Erschler group
Karthika Rajeev, Anitha Thillaisundaram
Francoeur and Garrido recently provided the first explicit examples of finitely generated branch groups with maximal subgroups of infinite index, where one of their examples is the…
Real-space quantum-to-classical transition of time dependent background fluctuations
S. Mahesh Chandran, Karthik Rajeev, S. Shankaranarayanan
Understanding the emergence of classical behavior from a quantum theory is vital to establishing the quantum origin for the temperature fluctuations observed in the Cosmic Microwav…
Effective-one-body formalism for leading-order radiative effects in the post-linear framework
Karthik Rajeev, S. Shankaranarayanan
In recent years, significant progress has been made in the computation of conservative and dissipative scattering observables using the post-Minkowskian approach to gravitational d…
New Kind of Echo from Quantum Black Holes
Sreenath K. Manikandan, Karthik Rajeev
We propose that a quantum black hole can produce a new kind of late-time gravitational echoes, facilitated by a near-horizon process analogous to Andreev reflection in condensed ma…
Wave function of the Universe as a sum over eventually inflating universes
Karthik Rajeev
We consider a proposal to define the wave function of the Universe as a sum over spacetimes that eventually inflate. In the minisuperspace model, we explicitly show that a simple f…
Maximal subgroups of a family of iterated monodromy groups
Karthika Rajeev, Anitha Thillaisundaram
The Basilica group is a well-known 2-generated weakly branch, but not branch, group acting on the binary rooted tree. Recently a more general form of the Basilica group has been in…
Bouncing with shear: Implications from quantum cosmology
Karthik Rajeev, Vikramaditya Mondal, Sumanta Chakraborty
We consider the introduction of anisotropy in a class of bouncing models of cosmology. The presence of anisotropy often spells doom on bouncing models, since the energy density due…
Lorentzian worldline path integral approach to Schwinger effect
Karthik Rajeev
We demonstrate that the positive frequency modes for a complex scalar field in a constant electric field (Schwinger modes), in three different gauges, can be represented as exact L…
On the Basilica Operation
Jan Moritz Petschick, Karthika Rajeev
Inspired by the Basilica group , we describe a general construction which allows us to associate to any group of automorphisms of a roote…
No-boundary Wave Function, Wheeler-DeWitt Equation and Path Integral Analysis of the Bouncing `Quantum' Cosmology
Karthik Rajeev, Vikramaditya Mondal, Sumanta Chakraborty
Bouncing models are alternatives to inflationary cosmology that replace the initial Big-Bang singularity by a `bouncing' phase. A deeper understanding of the initial conditions of…
Complex time route to quantum backreaction
Karthik Rajeev
We consider the backreaction of a quantum system on an effectively classical degree of freedom that is interacting with it. The backreaction equation based on the standard…
Exploring the Rindler vacuum and the Euclidean Plane
Karthik Rajeev, T. Padmanabhan
In flat spacetime, two inequivalent vacuum states which arise rather naturally are the Rindler vacuum (R) and the Minkowski vacuum (M). We disuss several aspects of the Rindler vac…
Generalized Schwinger effect and particle production in an expanding universe
Karthik Rajeev, Sumanta Chakraborty, T. Padmanabhan
We discuss several aspects of particle production in: (a) time dependent electric field and (b) expanding Friedmann background. In the first part of the paper, we provide an algebr…
Quantum Correlators in Friedmann Spacetimes -The omnipresent de Sitter and the invariant vacuum noise
Kinjalk Lochan, Karthik Rajeev, Amit Vikram +1
We discuss several aspects of quantum field theory of a scalar field in a Friedmann universe, clarifying and highlighting several conceptual and technical issues. (A) We show that…
A comment on generalized Schwinger effect
Karthik Rajeev, Sumanta Chakraborty, T. Padmanabhan
A spatially homogeneous, time-dependent, electric field can produce charged particle pairs from the vacuum. When the electric field is constant, the mean number of pairs which are…
Inverting a normal harmonic oscillator: Physical interpretation and applications
Karthik Rajeev, Sumanta Chakraborty, T. Padmanabhan
A harmonic oscillator with time-dependent mass and a time-dependent (squared) frequency occurs in the modelling of several physical systems. It is generally believe…
An approach to the quantization of black-hole quasi-normal modes
Soham Pal, Karthik Rajeev, S. Shankaranarayanan
In this work we derive the asymptotic quasi-normal modes of a BTZ black hole using a quantum field theoretic Lagrangian. The BTZ black hole is a very popular system in the context…