arXiv subjects

Nirmalya Kajuri

Publications and source records attributed to Nirmalya Kajuri.

29 records · Page 2Linked to original sources

arXiv2018

Bulk-boundary dictionary for a non local bulk field

AdS/CFT correspondence gives us a bulk-boundary dictionary between CFT operators and local fields in the bulk. Can a bulk-boundary dictionary exist for a non local bulk field? In this paper we consider a particular non local theory and show that a bulk boundary dictionary relating it to CFT operators in the bulk can indeed be constructed. In this dictionary the scale of non locality of the bulk theory is related to the conformal dimension of the dual CFT operator.

hep-th↗

arXiv2018

Hawking radiation in Non local field theories

Locality plays a key role in the derivation of Hawking radiation. Could relaxing the locality criterion modify Hawking radiation? We consider Hawking radiation in a general class of non local quantum field theories. We prove that Hawking radiation is unmodified for these theories. Our result establishes the universality of Hawking radiation in a larger class of theories.

gr-qc↗

arXiv2017

Low Energy Lorentz Violation in Polymer Quantization Revisited

In previous work, it had been shown that polymer quantized scalar field theory predicts that even an inertial observer can experience spontaneous excitations. This prediction was shown to hold at low energies. However, in these papers it was assumed that the polymer scale is constant. But it is possible to relax this condition and obtain a larger class of theories where the polymer scale is a function of momentum. Does the prediction of low energy Lorentz violation hold for all of these theories? In this paper we prove that it does. We also obtain the modified rates of radiation for some of these theories.

gr-qc↗

arXiv2017

Response of a rotating detector coupled to a polymer quantized field

Assuming that high energy effects may alter the standard dispersion relations governing quantized fields, the influence of such modifications on various phenomena has been studied extensively in the literature. In different contexts, it has generally been found that, while super-luminal dispersion relations hardly affect the standard results, sub-luminal relations can lead to (even substantial) modifications to the conventional results. A polymer quantized scalar field is characterized by a series of modified dispersion relations along with suitable changes to the standard measure of the density of modes. Amongst the modified dispersion relations, one finds that the lowest in the series can behave sub-luminally over a small domain in wavenumbers. In this work, we study the response of a uniformly rotating Unruh-DeWitt detector that is coupled to a polymer quantized scalar field. While certain sub-luminal dispersion relations can alter the response of the rotating detector considerably, in the case of polymer quantization, due to the specific nature of the dispersion relations, the modification to the transition probability rate of the detector does not prove to be substantial. We discuss the wider implications of the result.

gr-qc↗

arXiv2017

The time measurement problem in quantum cosmology

In the canonical approach to quantization of gravity, one often uses relational clock variables and an interpretation in terms of conditional probabilities to overcome the problem of time. In this essay we show that these suffer from serious conceptual issues.

gr-qc↗

arXiv2017

Unruh Effect in non local field theories

We study Unruh effect for a wide class of non local theories. Using the approach of Bogoliubov coefficents we show that Unruh effect remains entirely unmodified in these theories. However, for those non local theories which incorporate a minimal length, the approach using Unruh-DeWitt detectors predicts a modification in Unruh effect. Previous work shows that this modification may even be drastic. This appears contradictory, with two apparently equivalent methods giving different results. We investigate the origin of the contradiction and show that for these theories, the two methods are indeed inequivalent. We argue that the detector method incorporates an assumption of local interaction that does not hold for non local theories and therefore the method of Bogoliubov coefficients is preferable.

gr-qc↗

arXiv2016

Strong Equivalence Principle in Polymer Quantum Mechanics and deformed Heisenberg Algebra

The Strong equivalence Principle (SEP) states that the description of a physical system in a gravitational field is indistinguishable from the description of the same system at rest in an accelerating frame. While this statement holds true in both General Relativity and ordinary Quantum Mechanics, one expects it to fail when quantum gravity corrections are taken into account. In this paper we investigate the possible failure of the SEP in two Quantum Gravity inspired modifications of Quantum Mechanics - Polymer Quantum Mechanics and deformed Heisenberg Algebra. We find that the SEP fails to hold in both these theories. We estimate the deviation from SEP and find in both cases that it is too small to be measured in present day experiments.

gr-qc↗

arXiv2016

How is Lorentz Invariance encoded in the Hamiltonian?

One of the disadvantages of the Hamiltonian formulation is that Lorentz invariance is not manifest in the former. Given a Hamiltonian, there is no simple way to check whether it is relativistic or not. One would either have to solve for the equations of motion or calculate the Poisson Brackets of the Noether charges to perform such a check. In this paper we show that, for a class of Hamiltonians, it is possible to check Lorentz invariance directly from the Hamiltonian. Our work is particularly useful for theories where the other methods may not be readily available.

gr-qc↗

arXiv2016

Polymer Quantization predicts radiation in inertial frames

We investigate the response of an Unruh-DeWitt detector coupled to a polymer quantized massless scalar field in flat spacetime, using the propagator obtained by Hossain, Husain and Seahra. As this propagator violates Lorentz invariance, frames moving at different constant velocities are no longer equivalent. This means that it is possible in principle for even an observer moving at constant velocity to detect radiation. We show that such an observer indeed detects radiation. Remarkably, we show that the rate of this radiation does not decrease with the decrease in the characteristic length scale of polymer quantization. Thus the radiation cannot be suppressed by making the polymer length scale arbitrarily small. Our results should bring this theory within the ambit of low-energy experiments and place a lower limit on the characteristic polymer length scale.

gr-qc↗

arXiv2015

Path Integral representation for Polymer Quantized Scalar Fields

According to loop quantum gravity, matter fields must be quantized in a background independent manner. For scalar fields, such a background independent quantization is called polymer quantization and is inequivalent to the standard Schrodinger quantization. It is therefore important to obtain predictions from the polymer quantized scalar field theory and compare with the standard results. As a step towards this, we develop a path integral representation for the polymer quantized scalar field. We notice several crucial differences from the path integral for the schrodinger quantized scalar field. One important difference is the appearance of an extra summation at each point in the path integral for the polymer quantized theory. A second crucial difference is the loss of manifest Lorentz symmetry for a polymer quantized theory on Minkowski Space.

gr-qc↗

arXiv2013

Polymer quantization and Symmetries

Polymer quantization was discovered during the construction of Loop Quantum Cosmology. For the simplest quantum theory of one degree of freedom, the implications for dynamics were studied for the harmonic oscillator as well as some other potentials. For more degrees of freedom, the possibility of continuous, kinematic symmetries arises. While these are realised on the Hilbert space of polymer quantum mechanics, their infinitesimal versions are not supported. For an invariant Hamiltonian, these symmetry realizations imply infinite degeneracy suggesting that the symmetry should be spontaneously or explicitly broken. The estimation of symmetry violations in some cases have been analysed before. Here we explore the alternative of shifting the arena to the distributional states. We discuss both the polymer quantum mechanics case as well as polymer quantized scalar field.

gr-qc↗