154 citations · 692 across the 20 of their papers we have counts for
20 papers
Deviations from Gaussian White Noise in Stochastic Inflation
Zahra Ahmadi, Mahdiyar Noorbala
Stochastic inflation is widely used as a framework to study scalar field perturbations on an inflationary spacetime in a classical manner. In Starobinsky's seminal work and most of…
Classicality of Stochastic Noise Away From Quasi-de Sitter Inflation
Mahdiyar Noorbala
It is well known that a coarse-grained scalar field living on a de~Sitter (dS) background exhibits classical stochastic behavior, driven by a noise whose amplitude is set by the Hu…
Tail diversity from inflation
Sina Hooshangi, Mohammad Hossein Namjoo, Mahdiyar Noorbala
The tail of the distribution of primordial fluctuations (corresponding to the likelihood of realization of large fluctuations) is of interest, from both theoretical and observation…
Quantum Diffusion in Sharp Transition to Non-Slow-Roll Phase
Nahid Ahmadi, Mahdiyar Noorbala, Niloufar Feyzabadi +2
Transitions between different inflationary slow-roll scenarios are known to provide short non-slow-roll periods with non-trivial consequences. We consider the effect of quantum dif…
Rare Events Are Nonperturbative: Primordial Black Holes From Heavy-Tailed Distributions
Sina Hooshangi, Mohammad Hossein Namjoo, Mahdiyar Noorbala
In recent years it has been noted that the perturbative treatment of the statistics of fluctuations may fail to make correct predictions for the abundance of primordial black holes…
Stochastic non-attractor inflation
Hassan Firouzjahi, Amin Nassiri-Rad, Mahdiyar Noorbala
We extend the formalism of stochastic inflation to the setup of non-attractor inflation with a sound speed . We obtain the Langevin equations for the superhorizon perturbation…
Boundary Crossing in Stochastic Inflation with Critical Number of Fields
Mahdiyar Noorbala, Hassan Firouzjahi
We study boundary crossing probability in the context of stochastic inflation. We prove that for a generic multi-field inflationary potential, the probability that the inflaton rea…
Stochastic Ultra Slow Roll Inflation
Hassan Firouzjahi, Amin Nassiri-Rad, Mahdiyar Noorbala
We study the ultra slow roll model in the context of stochastic inflation. Using stochastic formalism, we calculate the mean number of -folds, the power spectrum, the bispe…
Tunneling in Stochastic Inflation
Mahdiyar Noorbala, Vincent Vennin, Hooshyar Assadullahi +2
The relative probability to decay towards different vacua during inflation is studied. The calculation is performed in single-field slow-roll potentials using the stochastic inflat…
SpaceTime from Hilbert Space: Decompositions of Hilbert Space as Instances of Time
Mahdiyar Noorbala
There has been recent interest in identifying entanglement as the fundamental concept from which space may emerge. We note that the particular way that a Hilbert space is decompose…
Is conserved along light path?
Mahdiyar Noorbala, Reza Sepehrinia
Snell's law states that the quantity is unchanged in refraction of light passing from one medium to another. We inquire whether this is true in the general case where the…
Critical Number of Fields in Stochastic Inflation
Vincent Vennin, Hooshyar Assadullahi, Hassan Firouzjahi +2
Stochastic effects in generic scenarios of inflation with multiple fields are investigated. First passage time techniques are employed to calculate the statistical moments of the n…
Multiple Fields in Stochastic Inflation
Hooshyar Assadullahi, Hassan Firouzjahi, Mahdiyar Noorbala +2
Stochastic effects in multi-field inflationary scenarios are investigated. A hierarchy of diffusion equations is derived, the solutions of which yield moments of the numbers of inf…
QED without Gauge Fields
Mahdiyar Noorbala
We begin by studying a very simple Hamiltonian for Maxwell's equations that has no gauge fields and is made entirely of the electromagnetic fields. We then show that this theory ca…
On the Second Law of Thermodynamics: The Significance of Coarse-Graining and the Role of Decoherence
Mahdiyar Noorbala
We take up the question why the initial entropy in the universe was small, in the context of evolution of the entropy of a classical system. We note that coarse-graining is a an im…
Leptogenesis in Inflationary models with Non-Abelian Gauge Fields
Azadeh Maleknejad, Mahdiyar Noorbala, M. M. Sheikh-Jabbari
A scenario of leptogenesis was introduced in [1] which works during inflationary period within standard model of particle physics setup. In this scenario lepton number is created b…
Effects of Variable Newton Constant During Inflation
Ali Akbar Abolhasani, Hassan Firouzjahi, Mahdiyar Noorbala
In this paper the effects of time-dependent Newton constant G during inflation are studied. We present the formalism of curvature perturbations in an inflationary system with a tim…
Observational consequences of chaotic inflation with nonminimal coupling to gravity
Andrei Linde, Mahdiyar Noorbala, Alexander Westphal
Recently there was an extensive discussion of Higgs inflation in the theory with the potential λ(ϕ^2-v^2)^2 and nonminimal coupling to gravity {ξ\over 2}ϕ^2R, for ξ>> 1 and v<< 1.…
Geocentric cosmology: a new look at the measure problem
Mahdiyar Noorbala, Vitaly Vanchurin
We show that most of cutoff measures of the multiverse violate some of the basic properties of probability theory when applied repeatedly to predict the results of local experiment…
Boltzmann brains and the scale-factor cutoff measure of the multiverse
Andrea De Simone, Alan H. Guth, Andrei Linde +3
To make predictions for an eternally inflating "multiverse", one must adopt a procedure for regulating its divergent spacetime volume. Recently, a new test of such spacetime measur…