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TOPIC: Inflation


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RE: Inflation
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Title: Inflation with a Weyl term, or ghosts at work
Authors: Nathalie Deruelle, Misao Sasaki, Yuuiti Sendouda, Ahmed Youssef

In order to assess the role of ghosts in cosmology, we study the evolution of linear cosmological perturbations during inflation when a Weyl term is added to the action. Our main result is that vector perturbations can no longer be ignored and that scalar modes diverge in the newtonian gauge but remain bounded in the comoving slicing.

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Title: Particles and gravitons creation after inflation from a 5D vacuum
Authors: Mariano Anabitarte, Mauricio Bellini (Mar del Plata University, IFIMAR - CONICET)

We use the Bogoliubov formalism to study both, particles and gravitons creation at the reheating stage, after an abrupt phase transition from inflation to a radiation dominated universe. The modes of the inflaton field fluctuations and the scalar fluctuations of the metric at the end of inflation are obtained by using a recently introduced formalism related to the Induced Matter theory of gravity. The interesting result is that the number of created particles is bigger than 10^{97} on cosmological scales. Furthermore, the number of gravitons are nearly 10^{-24} times smaller than the number of created particles. In both the cases, these numbers increases strongly when increases the scale.

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Title: Exploring a string-like landscape
Authors: Jonathan Frazer, Andrew R Liddle
(Version v2)

We explore inflationary trajectories within randomly-generated two-dimensional potentials, considered as a toy model of the string landscape. Both the background and perturbation equations are solved numerically, the latter using the two-field formalism of Peterson and Tegmark which fully incorporates the effect of isocurvature perturbations. Sufficient inflation is a rare event, occurring for only roughly one in 10^5 potentials. For models generating sufficient inflation, we find that the majority of runs satisfy current constraints from WMAP. The scalar spectral index is less than 1 in all runs. The tensor-to-scalar ratio is below the current limit, while typically large enough to be detected by next-generation CMB experiments and perhaps also by Planck. In many cases the inflationary consistency equation is broken by the effect of isocurvature modes.

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Title: Higgs Chaotic Inflation
Authors: Kazunori Nakayama, Fuminobu Takahashi

We construct a chaotic inflation model in which the Higgs fields play the role of the inflaton in the singlet extension of the supersymmetric standard model. The key idea is to impose a shift symmetry on the D-flat direction Hu Hd in the Kahler potential. The model is a realisation of the recently proposed running kinetic inflation, in which the coefficient of the kinetic term grows as the inflaton field. The inflaton potential depends on the structure of the Higgs sector. For instance, the inflaton potential is proportional to phi^{2/3} during inflation in the NMSSM.

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Did the big bang boil? The birth of our universe could have seethed with hot bubbles and, perhaps, a second period of rapid expansion. Such an episode may have left an imprint on the universe that persists to this day and might mean we're on the wrong track in our hunt for dark matter.
Just 10^-37 seconds or so after its birth, a period of inflation is thought to have caused the universe to balloon in size. This process is thought to have amplified tiny quantum fluctuations in the vacuum, giving rise to the megastructures we see all around us in the universe today.
A second profound transformation is thought to have followed hot on the heels of inflation. Just microseconds old and at trillions of degrees, the universe condensed from a superhot soup of sub-nuclear particles called a quark-gluon plasma (QGP) into particles such as protons and neutrons. But exactly how this happened is far from clear.

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Astrophysicist, team win stimulus grant to build telescope

A team led by a Johns Hopkins astrophysicist has won a $5 million National Science Foundation grant - administered through the stimulus act - to build an instrument designed to probe what happened during the universe's first trillionth of a second, when it suddenly grew from submicroscopic to astronomical size in far less time than it takes to blink your eye.
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New Sensors to Test Inflationary Universe Theory
The National Institute of Standards and Technology (NIST) has teamed up with Princeton University, the University of Colorado at Boulder, and the University of Chicago to create new sensors capable of detecting much weaker microwaves than those captured by any existing sensors. The new sensors will be used in experiments to measure the Cosmic Microwave Background (CMB), a very weak background energy believed to be a remnant of the Big Bang.
The novel sensors are not only used to detect the CMB, but will also attempt to measure the polarisation of the microwaves, specifically looking for a certain type of polarisation called B-Mode polarisation. If found, such polarisation would prove that cosmic inflation occurred immediately after the Big Bang. Such inflation would emit gravitational waves, which will cause the polarisation of the CMB.

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QUIET
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A tiny fraction of a second following the big bang, the universe allegedly experienced the most inflationary period it has ever known.
During this inflationary era, space expanded faster than the speed of light. It sounds crazy, but it fits a variety of cosmological observations made in recent years, said University of Chicago physicist Bruce Winstein.

"Theorists take it to be true, but we have to prove it. It needs a real test, and that test is whether or not gravity waves were created" - Bruce Winstein, the Samuel K. Allison Distinguished Service Professor in Physics at the University of Chicago.

Winstein and his Chicago associates are part of the international QUIET (Q/U Imaging ExperimenT; the Q and U stand for radiation parameters called Stokes parameters) collaboration that has devised such a test.

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Cosmic inflation
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A telescope at the South Pole is being fine tuned to search for gravity waves, hypothetical distortions of space-time that, if confirmed to exist, could further validate Einstein and reveal convincing evidence for a big cosmology theory.
Cosmic inflation theory proposes that the early universe passed through a phase of exponential expansion, ballooning almost instantaneously from less than the size of an atom to about golf-ball size.

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Primordial light
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During the next decade, some cosmologists say a delicate measurement of primordial light could reveal evidence for the cosmic inflation hypothesis, which proposes that a random, microscopic density fluctuation in the fabric of space gave birth to the universe in a hot big bang approximately 13.7 billion years ago - it also predicts the existence of an infinite number of universes.   The hypothesis was first proposed by Alan Guth of the Massachusetts Institute of Technology in 1979 but cosmologists currently have no way of testing this prediction.

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