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The cosmic string theory for cosmological fluctuations is a good example of healthy scientific progress in cosmology. It is a well defined physically motivated model that has been tested by cosmological observations and has been ruled out…
Helical intergalactic magnetic fields at the $\sim 10^{-14}~{\rm G}$ level on $\sim 10~{\rm Mpc}$ length scales are indicated by current gamma ray observations. The existence of magnetic fields in cosmic voids and their non-trivial helicity…
It is usually assumed that when Weyl invariance is unbroken in the electromagnetic sector, the energy density of primordial magnetic fields will redshift as radiation. Here we show that primordial magnetic fields do not exhibit…
Introducing a variable cosmological parameter $\Lambda (t)$ in a geometrical manner from a 5D Riemann-flat metric, we investigate the origin and evolution of primordial magnetic fields in the early universe, when the expansion is governed…
We present a brief review of Cosmological Inflation from the personal perspective of the author who almost 30 years ago proposed a way of resolving the problem of Cosmological Horizon by employing certain notions and developments from the…
We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints…
Magnetic fields are observed everywhere in the universe. In this review, we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects. Readers can follow the milestones in the observations of…
We discuss the cosmological evolution of matter sources with small anisotropic pressures. This includes electric and magnetic fields, collisionless relativistic particles, gravitons, antisymmetric axion fields in low-energy string…
Recently Hollands and Wald argued that inflation does not solve any of the major cosmological problems. We explain why we disagree with their arguments. They also proposed a new speculative mechanism of generation of density perturbations.…
I argue that cosmological data from the epoch of primordial inflation is catalyzing the maturation of quantum gravity from speculation into a hard science. I explain why quantum gravitational effects from primordial inflation are…
In this paper, we investigate the evolution of the early universe within an emergent fractional cosmological framework. The underlying formulation is conceptually rooted in generalized measure constructions, closely related to fractal…
I show that the problem of realizing inflation in theories with random potentials of a limited number of fields can be solved, and agreement with the observational data can be naturally achieved if at least one of these fields has a…
This review article aims at presenting the theory of inflation. We first describe the background spacetime behavior during the slow-roll phase and analyze how inflation ends and the Universe reheats. Then, we present the theory of…
We revisit the mechanism of helical magnetogenesis during inflation with a parity violating interaction using the formalism of stochastic inflation. One of the polarization of the gauge field undergoes tachyonic growth leading to the…
Does inflation provide a compelling explanation for why the universe is so large, so flat, and so old, and a predictive theory of density perturbations? In this brief contribution (based on the role of the author as moderator of the…
Primordial magnetic fields of cosmologically interesting field strengths can be generated from gravitationally coupled electrodynamics during inflation. As the cosmological constraints require this to be power law inflation it is not…
The main aim of this paper is to provide a qualitative introduction to the cosmic inflation and its relationship with current cosmological observations. The inflationary model solves many of the fundamental problems that challenge the…
We argue that the dynamics of photons canonically coupled to scalars in de Sitter inflation gets modified by a photon mass term. This might have lead to generation of potentially observable magnetic field correlated over cosmological scales…
We study the generation of magnetic fields in the Higgs inflation model with the axial coupling in order to break the conformal invariance of the Maxwell action and produce strong magnetic fields. We consider radiatively corrected Higgs…
This paper contains a critique of the standard inflationary account of the origin of cosmological structures from quantum fluctuations in the early universe. This critique can be thought to be purely philosophical in nature, but I prefer to…