## About

246

Publications

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Introduction

I work on Quantum Gravity (theory and phenomenology), Cosmology (singularities, dark matter and energy, inflation, modified Newtonian dynamics), and Foundations of Quantum Mechanics.

Additional affiliations

July 2013 - present

July 2008 - June 2013

June 2003 - June 2008

## Publications

Publications (246)

We study the superradiance of anyons from (2 + 1)-dimensional Banados, Teitelboim, and Zanelli (BTZ) black hole. We discuss the possibility of observing of this phenomenon in analogue black holes.

A bouncing Universe avoids the big-bang singularity. Using the time-like and null Raychaudhhuri equations, we explore whether the bounce near the big-bang, within a broad spectrum of modified theories of gravity, allows for cosmologically relevant power-law solutions under reasonable physical conditions. Our study shows that certain modified theori...

We derive the quasinormal modes of anyons for (2+1)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(2+1)$$\end{document}-dimensional Bañados, Teitelboim, and Zanelli (B...

The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological app...

A consistent theory of quantum gravity will require a fully quantum formulation of the classical equivalence principle. Such a formulation has been recently proposed in terms of the equality of the rest, inertial and gravitational mass operators, and for non-relativistic particles in a weak gravitational field. In this work, we propose a generaliza...

A consistent theory of quantum gravity will require a fully quantum formulation of the classical equivalence principle. Such a formulation has been recently proposed in terms of the equality of the rest, inertial and gravitational mass operators, and for non-relativistic particles in a weak gravitational field. In this work, we propose a generaliza...

A possibility to describe quantum gravitational fluctuations of the spacetime background is provided by virtual D-branes. These effects may induce a tiny violation of the Lorentz invariance (as well as a possible violation of the equivalence principle). In this framework, we study the formation of light elements in the early Universe (Big Bang Nucl...

A possibility to describe quantum gravitational fluctuations of the spacetime background is provided by virtual $D$-branes. These effects may induce a tiny violation of the Lorentz invariance (as well as a possible violation of the equivalence principle). In this framework, we study the formation of light elements in the early Universe (Big Bang Nu...

Several phenomenological approaches to quantum gravity predict the existence of a minimal measurable length and/or a maximum measurable momentum near the Planck scale. When embedded into the framework of quantum mechanics, such constraints induce a modification of the canonical commutation relations and thus a generalization of the Heisenberg uncer...

The generalized uncertainty principle (GUP) is predicted by most theories of quantum gravity and in turn introduces a minimum measurable length in nature. It was also shown recently that GUP predicts potentially measurable corrections to the “doubling time” of freely moving Gaussian atomic and molecular wave packets with a favorable combination of...

The mass of an astrophysical object can be estimated by the amount of gravitational lensing of another object that it causes. To arrive at the estimation however, one assumes the validity of the inverse square law of gravity, or equivalently an attractive $1/r$ potential. We show that the above, augmented by a logarithmic potential at galactic leng...

The mass of an astrophysical object can be estimated by the amount of gravitational lensing of another object that it causes. To arrive at the estimation however, one assumes the validity of the inverse square law of gravity, or equivalently an attractive 1/r potential. We show that the above, augmented by a logarithmic potential at galactic length...

In classical gravity, nothing can escape from a black hole, not even light. In particular, this happens for stationary black holes because their horizons are null. We show, on the other hand, that the apparent horizon and the region near r = 0 of an evaporating charged, rotating black hole are both timelike. This implies that there exists a channel...

We investigate the quasinormal modes of a massless scalar field in a Schwarzschild black hole, which is deformed due to noncommutative corrections. We present the deformed Schwarzschild black hole solution, which depends on the noncommutative parameter $\Theta$, and we extract the master equation as a Schr\"odinger-like equation, giving the explici...

The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundament...

A recent study established a correspondence between the Generalized Uncertainty Principle (GUP) and Modified theories of gravity, particularly Stelle gravity. We investigate the consequences of this correspondence for inflation and cosmological observables by evaluating the power spectrum of the scalar and tensor perturbations using two distinct me...

It has recently been shown that any observed potential can in principle be generated via quantum mechanics using a suitable wave function. In this work, we consider the concrete example of the gravitational potential experienced by a test particle at length scales spanning from the planetary to the cosmological, and determine the wave function that...

The Generalized Uncertainty Principle (GUP) is a modification of Heisenberg's Uncertainty Principle predicted by several theories of quantum gravity. In this work, we compute GUP corrections to the well-known Jaynes-Cummings Model (JCM) with the aim of eventually observing quantum gravity effects in quantum optical systems. To this end, we first an...

In this essay, we show that Newton’s gravitational potential, augmented by a logarithmic term, partly or wholly mitigates the need for dark matter. As a bonus, it also explains why MOND seems to work at galactic scales. We speculate on the origin of such a potential.

We derive the quasinormal modes of anyons from (2+1)-dimensional Banados, Teitelboim, and Zanelli(BTZ) and analogue black holes, and discuss potential experiments to measure these quasinormal modes.

It has recently been shown that any observed potential can in principle be generated via quantum mechanics using a suitable wavefunction. In this work, we consider the concrete example of the gravitational potential experienced by a test particle at length scales spanning from the planetary to the cosmological, and determine the wavefunction that w...

A recent study established a correspondence between the Generalized Uncertainty Principle (GUP) and Modified theories of gravity, particularly Stelle gravity. We investigate the consequences of this correspondence for inflation and cosmological observables by evaluating the power spectrum of the scalar and tensor perturbations using two distinct me...

The Experiment to Detect the Global Epoch of Reionisation Signature (EDGES) collaboration has recently reported an important result related to the absorption signal in the Cosmic Microwave Background radiation spectrum. This signal corresponds to the red-shifted 21-cm line at $$z \simeq 17.2$$ z ≃ 17.2 , whose amplitude is about twice the expected...

The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundament...

We review, as well as provide some new results regarding the study of the structure of spacetime and the singularity in the interior of the Schwarzschild black hole in both loop quantum gravity and generalized uncertainty principle approaches, using congruences and their associated expansion scalar and the Raychaudhuri equation. We reaffirm previou...

Black holes are conjectured to be the fastest quantum scramblers in nature, with the stretched horizon being the scrambling boundary. Under this assumption, we show that any infalling body must couple to virtually the entire black hole Hilbert space even prior to the Page time in order for there to be any hope of preserving the often-cited claim of...

We show that Newton's gravitational potential, augmented by a logarithmic term, partly or wholly mitigates the need for dark matter. As a bonus, it also explains why MOND seems to work at galactic scales. We speculate on the origin of such a potential.

Theories of Quantum Gravity predict a minimum measurable length and a corresponding modification of the Heisenberg Uncertainty Principle to the so-called Generalized Uncertainty Principle (GUP). However, this modification is usually formulated in non-relativistic language, making it unclear whether the minimum length is Lorentz invariant. We have f...

We review, as well as provide some new results regarding the study of the structure of spacetime and the singularity in the interior of the Schwarzschild black hole in both loop quantum gravity and generalized uncertainty principle approaches, using congruences and their associated expansion scalar and the Raychaudhuri equation. We reaffirm previou...

The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundament...

The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravitational-wave backgrounds and their implications for early universe and particle physics, from the MeV to the Planck scale. However, the range of potential cosmological app...

We examine the viability of cosmological solution(s) describing a unified picture of the dark side of the universe from a Bose-Einstein condensate (BEC) of light bosons. The energy density of the BEC, together with its quantum potential, can indeed account for such a unification, in the sense that the (dust-like) cold dark matter and the dark energ...

The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give u...

The fundamental constituents of the nucleus are charged protons and neutral neutrons. They are bound together by the strong force into stable and unstable nuclei. Stability requires the right number of neutrons for a given number of protons, but many unstable isotopes exist in nature. We describe the various forms of radioactivity that allow these...

In 1915, ten years after his discovery of the special theory of relativity, Albert Einstein extended his Fundamental Postulate to include all observers, not just those in inertial frames. The result was the general theory of relativity that produced the second major paradigm shift of the early 20th century. Spacetime was transformed from the rigid...

Symmetry plays an important role in art and aesthetics: paintings, buildings and faces are more pleasing to the eye if they have some symmetry, but not too much. In physics, too, theories and objects that have a high degree of symmetry are preferred for their simplicity and their elegance. For symmetry to be a useful concept in physics, however, it...

Special relativity and quantum mechanics form the foundation of twenty-first century physics. At the risk of abusing a metaphor, symmetry is the rebar, or supporting steel, that threads through this foundation, providing strength and allowing a simplicity of form that would be otherwise unachievable. In this chapter we introduce the concept of symm...

This chapter provides concrete tools for studying and using symmetries in physics. We start by reviewing vectors and then go on to discuss the linear transformations that correspond to spatial translations, rotations and reflections. Next we describe the deep connection between symmetry operations and linear transformations. The key point is that s...

We address the issue of time evolution of states in quantum mechanics. We define stationary states in analogy with standing waves on a string and derive the time independent Schrödinger equation (SE) for the wave function of a particle with fixed energy moving in a potential well. Generically, the solutions to the SE can only be found if the quantu...

Quantum mechanics has fascinating and sometimes weird consequences. The so-called EPR conundrum first raised by Einstein, Podolsky and Rosen in 1935 questions the completeness of quantum mechanics. The problem has its roots in the uncertainty principle, which prevents quantum states from describing simultaneously certain complementary elements of r...

The formulation of special relativity by Albert Einstein in 1905 was based on a symmetry assumption, namely that the laws of physics must be the same for all non-accelerating (i.e. inertial) observers. This simple and very sensible assumption, called the Fundamental Postulate of special relativity, led to one of the most important paradigm shifts i...

The quantum description of the state of a particle is drastically different from that of the Newtonian description. Instead of specifying the precise position and momentum of the particle, quantum mechanics describes its quantum state in terms of a wave function that assigns at every time a complex number to each point in space. We describe the pro...

Three phenomena greatly puzzled physicists at the turn of the twentieth century: the photoelectric effect, Compton scattering and the ultraviolet catastrophe associated with blackbody radiation. We show in detail how these puzzles led to the startling conclusion that light, previously thought of as a wave, can behave under certain circumstances as...

This chapter provides some details about some of the more important mathematics underlying quantum mechanics, including complex numbers, statistics, Fourier transforms and waves.

The general form of the Lorentz transformations that replace the Galilean transformations of Newtonian physics is presented. We discuss their interpretation in terms of the geometry of the spacetime continuum. The relativistic addition of velocities follows directly from the general Lorentz transformations and guarantees that all inertial observers...

We start with a brief classical description of the hydrogen atom including a supplementary section that reveals the hidden symmetry responsible in part for the incredibly simple structure of the energy spectrum of the hydrogen atom. Niel’s Bohr’s simple but incorrect derivation of the energy spectrum of the Hydrogen atom is then described. Although...

The Generalized Uncertainty Principle (GUP), which is a generalization of the familiar Heisenberg Uncertainty Principle, is predicted by most theories of quantum gravity, and in turn predicts a minimum measurable length in nature. GUP includes an undetermined parameter, whose allowed range has been suggested by various experiments, but whose precis...

The dynamics of a quantum particle is governed by its wavefunction, which in turn is determined by the classical potential to which it is subjected. However the wavefunction itself induces a quantum potential, the particle ‘sees’ the sum of the classical and quantum potentials, and there is no way to separate the two. Therefore in principle, part o...

The dynamics of a quantum particle is governed by its wavefunction, which in turn is determined by the classical potential to which it is subjected. However the wavefunction itself induces a quantum potential, the particle `sees' the sum of the classical and quantum potentials, and there is no way to separate the two. Therefore in principle, part o...

The unexplained observed baryon asymmetry in the Universe is a long-standing problem in physics, with no satisfactory resolution so far. To explain this asymmetry, three Sakharov conditions must be met. An interaction term which couples space-time and the baryon current is considered, which satisfies the first two Sakharov conditions. Furthermore,...

In this essay, we show that if one starts with a universe with some matter and a cosmological constant, then quantum mechanics naturally induces an attractive gravitational potential and an effective Newton’s coupling. Thus, gravity is an emergent phenomenon and what should be quantized are the fundamental degrees of freedom from which it emerges.

The Planck or the quantum gravity scale, being $16$ orders of magnitude greater than the electroweak scale, is often considered inaccessible by current experimental techniques. However, it was shown recently by one of the current authors that quantum gravity effects via the Generalized Uncertainty Principle affects the time required for free wavepa...

The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give u...

We derive the Hawking radiation spectrum of anyons, namely particles in (2+1)—dimension obeying fractional statistics, from a Bañados, Teitelboim, and Zanelli (BTZ) black hole, in the tunneling formalism. We examine ways of measuring the spectrum in experimentally realizable systems in the laboratory.

In classical gravity, nothing can escape from a black hole, not even light. In particular, this happens for stationary black holes because their horizons are null. We show, on the other hand, that the apparent horizon and the region near r = 0 of an evaporating charged, rotating black hole are both timelike. This implies that there exists a channel...

We study Quantum Gravity effects in cosmology, and in particular that of the Generalized Uncertainty Principle on the Friedmann equations. We show that the Quantum Gravity induced variations of the energy density and pressure in the radiation dominated era provide a viable explanation of the observed baryon asymmetry in the Universe.

Several theories of quantum gravity propose the existence of a minimal measurable length and maximum measurable momentum near the Planck scale. When integrated into the framework of quantum mechanics, such restrictions lead to the generalization of the Heisenberg uncertainty principle, which is commonly referred to as the generalized uncertainty pr...

We show that loop quantum gravity effects leads to the finiteness of expansion and its rate of change in the effective regime in the interior of the Schwarzschild black hole. As a consequence the singularity is resolved.

The Experiment to Detect the Global Epoch of Reionisation Signature (EDGES) collaboration has recently reported an important result related to the absorption signal in the Cosmic Microwave Background radiation spectrum. This signal corresponds to the red-shifted 21-cm line at $z \simeq 17.2$, whose amplitude is about twice the expected value. This...

Black holes are unique among astrophysical sources: they are the simplest macroscopic objects in the Universe, and they are extraordinary in terms of their ability to convert energy into electromagnetic and gravitational radiation. Our capacity to probe their nature is limited by the sensitivity of our detectors. The LIGO/Virgo interferometers are...

Quantum theories of gravity predict interesting phenomenological features such as a minimum measurable length and maximum momentum. We use the Generalized Uncertainty Principle (GUP), which is an extension of the standard Heisenberg Uncertainty Principle motivated by Quantum Gravity, to model the above features. In particular, we use a GUP with mod...

A bstract
The classical Raychaudhuri equation predicts the formation of conjugate points for a congruence of geodesics, in a finite proper time. This in conjunction with the Hawking-Penrose singularity theorems predicts the incompleteness of geodesics and thereby the singular nature of practically all spacetimes. We compute the generic corrections...

We derive the Hawking radiation spectrum of anyons, namely particles in (2+1)-dimension obeying fractional statistics, from a BTZ black hole, in the tunneling formalism. We examine ways of measuring the spectrum in experimentally realizable systems in the laboratory.

We study quantum gravity effects on the density of states in statistical mechanics and its implications for the critical temperature of a Bose Einstein condensate and fraction of bosons in its ground state. We also study the effects of compact extra dimensions on the critical temperature and the fraction. We consider both neutral and charged bosons...

The unexplained observed baryon asymmetry in the Universe is a long-standing problem in physics, with no satisfactory resolution so far. To explain this asymmetry, three Sakharov conditions must be met. An interaction term which couples space-time and the baryon current is considered, which satisfies the first two Sakharov conditions. Furthermore,...

We show that the apparent horizon and the region near [Formula: see text] of an evaporating charged, rotating black hole are timelike. It then follows that black holes in nature, which invariably have some rotation, have a channel, via which classical or quantum information can escape to the outside, while the black hole shrinks in size. We discuss...

Quantum theories of gravity predict interesting phenomenological features such as a minimum measurable length and maximum momentum. We use the Generalized Uncertainty Principle (GUP), which is an extension of the standard Heisenberg Uncertainty Principle motivated by Quantum Gravity, to model the above features. In particular, we use a GUP with mod...

We compute bounds on the GUP parameters for two versions of GUP using gravitational wave data from the events GW150914 and GW190521. The speed of the graviton and photon are calculated in a curved spacetime modified by GUP, assuming that these particles have a small mass. The observational bound on the difference in their speeds translates to bound...

The classical Raychaudhuri equation predicts the formation of conjugate points for a congruence of geodesics, in a finite proper time. This in conjunction with the Hawking-Penrose singularity theorems predicts the incompleteness of geodesics and thereby the singular nature of practically all spacetimes. We compute the generic corrections to the Ray...

We show that if one starts with a Universe with some matter and a cosmological constant, then quantum mechanics naturally induces an attractive gravitational potential and an effective Newton's coupling. Thus gravity is an emergent phenomenon and what should be quantized are the fundamental degrees of freedom from which it emerges.

We show that the apparent horizon and the region near $r=0$ of an evaporating charged, rotating black hole are timelike. It then follows that for black holes in nature, which invariably have some rotation, have a channel, via which classical or quantum information can escape to the outside, while the black hole shrinks in size. We discuss implicati...

We derive loop quantum gravity corrections to the Raychaudhuri equation in the interior of a Schwarzschild black hole and near the classical singularity. We show that the resulting effective equation implies defocusing of geodesics due to the appearance of repulsive terms. This prevents the formation of conjugate points, renders the singularity the...

We derive loop quantum gravity corrections to the Raychaudhuri equation in the interior of a Schwarzschild black hole and near the classical singularity. We show that the resulting effective equation implies defocusing of geodesics due to the appearance of repulsive terms. This prevents the formation of conjugate points, renders the singularity the...

We study Quantum Gravity effects on the density of states in statistical mechanics and its implications for the critical temperature of a Bose Einstein Condensate and fraction of bosons in its ground state. We also study the effects of compact extra dimensions on the critical temperature and the fraction. We consider both neutral and charged bosons...

The Planck or the quantum gravity scale, being $16$ orders of magnitude greater than the electroweak scale, is often considered inaccessible by current experimental techniques. However, it was shown recently by one of the current authors that quantum gravity effects via the Generalized Uncertainty Principle affects the time required for free wavepa...

It has been shown beyond reasonable doubt that the majority (about 95%) of the total energy budget of the universe is given by dark components, namely Dark Matter and Dark Energy. What constitutes these components remains to be satisfactorily understood however, despite a number of promising candidates. An associated conundrum is that of the coinci...

It has been shown beyond reasonable doubt that the majority (about 95%) of the total energy budget of the universe is given by the dark components, namely Dark Matter and Dark Energy. What constitutes these components remains to be satisfactorily understood however, despite a number of promising candidates. An associated conundrum is that of the co...

We compute bounds on the GUP parameters for two versions of GUP using gravitational wave data from the events GW150914 and GW190521. The speed of the graviton and photon are calculated in a curved spacetime modified by GUP, assuming that these particles have a small mass. The observational bound on the difference in their speeds translates to bound...

We derive Loop Quantum Gravity corrections to the Raychaudhuri equation in the interior of a Schwarzschild black hole and near the classical singularity. We show that the resulting effective equation implies defocusing of geodesics due to the appearance of repulsive terms. This prevents the formation of conjugate points, renders the singularity the...

Continuing our earlier work on the application of the Relativistic Generalized Uncertainty Principle (RGUP) to quantum field theories, in this paper we study Quantum Electrodynamics (QED) with minimum length. We obtain expressions for the Lagrangian, Feynman rules and scattering amplitudes of the theory, and discuss their consequences for current a...

Recently, the authors presented a covariant extension of the Generalized Uncertainty Principle (GUP) with a Lorentz invariant minimum length. This opens the way for constructing and exploring the observable consequences of minimum length in Relativistic Quantum Field Theories. In particular, we compute quantum gravity corrections to high energy sca...

The quantum description of the state of a particle is drastically different from that of the Newtonian description. Instead of specifying the precise position and momentum of the particle, quantum mechanics describes its quantum state in terms of a wave function that assigns at every time a complex number to each point in space. We describe the pro...