scholarly journals BICEP/Keck and cosmological attractors

2021 ◽  
Vol 2021 (12) ◽  
pp. 008
Author(s):  
Renata Kallosh ◽  
Andrei Linde
Keyword(s):  
String Theory ◽  
Observational Data ◽  
Data Release ◽  
Inflationary Models ◽  
The Way

Abstract We discuss implications of the latest BICEP/Keck data release for inflationary models, with special emphasis on the cosmological attractors which can describe all presently available inflation-related observational data. These models are compatible with any value of the tensor to scalar ratio r, all the way down to r = 0. Some of the string theory motivated models of this class predict 10-3 ≤ r ≤ 10-2. The upper part of this range can be explored by the ongoing BICEP/Keck observations.

A class of inflaton potentials from RG analysis of scalar-gravity interaction

2014 ◽  
Vol 11 (02) ◽  
pp. 1460008
Author(s):  
Artur R. Pietrykowski
Keyword(s):  
Renormalization Group ◽  
Scalar Field ◽  
Observational Data ◽  
Particle Physics ◽  
Field System ◽  
Group Methods ◽  
Renormalization Group Methods ◽  
Scalar Gravity ◽  
Inflationary Models ◽  
The Way

Inflationary models are characterized by the form of a potential which is arbitrary and usually parametrized so as to match the observational data. However, making use of the renormalization group methods to a gravity-scalar field system it is possible to find physically nontrivial potentials that might be relevant for cosmology and particle physics as well. I will pinpoint the way this class of potentials may be found as well as discuss their utility for inflationary models.

Cosmic superstrings

2008 ◽  
Vol 366 (1877) ◽  
pp. 2881-2894 ◽  
Author(s):  
Mairi Sakellariadou
Keyword(s):  
String Theory ◽  
Observational Data ◽  
Cosmological Models ◽  
Brane World ◽  
Inflationary Model ◽  
Brane Inflation ◽  
Insight Into

Cosmic superstrings are expected to be formed at the end of brane inflation, within the context of brane-world cosmological models inspired from string theory. By studying the properties of cosmic superstring networks and comparing their phenomenological consequences against observational data, we aim to pin down the successful and natural inflationary model and get an insight into the stringy description of our Universe.

scholarly journals Key Issues: A Round Table Discussion

1993 ◽  
Vol 137 ◽  
pp. 776-786
Author(s):  
T.M. Brown ◽  
P. Demarque ◽  
R. Noyes ◽  
F. Praderie ◽  
I.W. Roxburgh ◽  
...  
Keyword(s):  
Observational Data ◽  
Round Table ◽  
The Other ◽  
Complete List ◽  
Round Table Discussion ◽  
Amount Of Information ◽  
Table Discussion ◽  
Key Issues ◽  
The Way

We have taken part to an exceptionally rich colloquium, characterized by a large amount of information in all fields of physics, and a remarkable collection of observational data. Our understanding of what is going on inside the stars has changed in a radical manner during the last years, on one side because the observations are bringing new kinds of information, and on the other side because theory in its development is taking into account a number of processes, some of them having been completely ignored only ten years ago.It is impossible to draw here a complete list of problems. There are many cases where some inconsistency could be found in the theory itself or some contradiction between observational data and theory. I recommended that such a list should be drawn carefully. The participants to the round table discussion will give their contribution, helping to open the way to new fields of research and to new discoveries.

scholarly journals QUANTIZING HIGHER-SPIN STRING THEORIES

1995 ◽  
Vol 10 (14) ◽  
pp. 2123-2142 ◽  
Author(s):  
H. LU ◽  
X.J. WANG ◽  
K.-W. XU ◽  
C.N. POPE ◽  
K. THIELEMANS
Keyword(s):  
String Theory ◽  
Classical Theory ◽  
Energy Momentum Tensor ◽  
Standard Form ◽  
Momentum Tensor ◽  
Minimal Models ◽  
Classical Level ◽  
Higher Spin ◽  
String Theories ◽  
The Way

In this paper, we examine the conditions under which a higher-spin string theory can be quantized. The quantizability is crucially dependent on the way in which the matter currents are realized at the classical level. In particular, we construct classical realizations for the W2,s algebra, which is generated by a primary spin-s current in addition to the energy-momentum tensor, and discuss the quantization for s≤8. From these examples we see that quantum BRST operators can exist even when there is no quantum generalization of the classical W2,s algebra. Moreover, we find that there can be several inequivalent ways of quantizing a given classical theory, leading to different BRST operators with inequivalent cohomologies. We discuss their relation to certain minimal models. We also consider the hierarchical embeddings of string theories proposed recently by Berkovits and Vafa, and show how the already known W strings provide examples of this phenomenon. Attempts to find higher-spin fermionic generalizations lead us to examine whether classical BRST operators for [Formula: see text](n odd) algebras can exist. We find that even though such fermionic algebras close up to null fields, one cannot build nilpotent BRST operators, at least of the standard form.

scholarly journals The physical states of the Hybrid Formalism

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Matthias R. Gaberdiel ◽  
Kiarash Naderi
Keyword(s):  
String Theory ◽  
Free Field ◽  
Vertex Operators ◽  
World Sheet ◽  
Brst Cohomology ◽  
The World ◽  
The Way

Abstract String theory on AdS3 × S3 × $$ \mathbbm{T} $$ T 4 with one unit (k = 1) of NS-NS flux is considered in the hybrid formalism of Berkovits, Vafa & Witten (BVW). Using the free field realisation of the world-sheet theory at k = 1, we identify explicitly the BRST cohomology classes corresponding to some of the low-lying states of the dual CFT. In particular, we do this for the $$ \mathcal{N} $$ N = 4 superconformal generators of the symmetric orbifold theory, and we confirm these identifications by showing that the worldsheet correlators reproduce the expected dual CFT answer. Along the way we note that the physical vertex operators on the worldsheet have a simpler form if one works with a different, but equivalent, choice for the BRST operators relative to BVW.

Physics of Galaxy Evolution

2013 ◽  
Author(s):  
Abraham Loeb ◽  
Steven R. Furlanetto
Keyword(s):  
Observational Data ◽  
Galaxy Evolution ◽  
Milky Way ◽  
Dwarf Galaxies ◽  
Theoretical Perspective ◽  
Building Blocks ◽  
Cosmic History ◽  
The Way

This chapter examines galaxies in some detail from a largely theoretical perspective. Along the way, one must bear in mind that, although the described progression of events in this chapter is plausible, at this time it is only a conjecture in the minds of theorists that has not yet been confirmed by observational data. This chapter therefore focuses only on the physics that drive these interstellar objects, showing how the earliest dwarf galaxies eventually merged and made bigger galaxies. A present-day galaxy like our own Milky Way was constructed over cosmic history by the assembly of a million building blocks in the form of the first dwarf galaxies.

scholarly journals On negative energies, strings, branes, and braneworlds: A review of novel approaches

2020 ◽  
Vol 35 (33) ◽  
pp. 2030020
Author(s):  
Matej Pavšič
Keyword(s):  
String Theory ◽  
Quantum Gravity ◽  
Extra Dimensions ◽  
Curved Spaces ◽  
Higher Derivative ◽  
Novel Approaches ◽  
The Way

On the way towards quantum gravity and the unification of interaction, several ideas have been rejected and avenues avoided because they were perceived as physically unviable. But in the literature there are works in which it was found the contrary, namely that those rejected topics make sense after all. Such topics, reviewed in this paper, are negative energies occurring in higher derivative theories and ultrahyperbolic spaces, ordering ambiguity of operators in curved spaces, the vast landscape of possible compactifications of extra dimensions in string theory, and quantization of a 3-brane in braneworld scenarios.

scholarly journals Ninebrane structures

2015 ◽  
Vol 12 (04) ◽  
pp. 1550041 ◽  
Author(s):  
Hisham Sati
Keyword(s):  
String Theory ◽  
Lower Degree ◽  
Topological Groups ◽  
Differential Cohomology ◽  
Spin Structures ◽  
M Theory ◽  
The Way

String structures in degree 4 are associated with cancelation of anomalies of string theory in 10 dimensions. Fivebrane structures in degree 8 have recently been shown to be associated with cancelation of anomalies associated to fivebranes in string theory and M-theory. We introduce and describe Ninebrane structures in degree 12 and demonstrate how they capture some anomaly cancelation phenomena in M-theory. Along the way we also define certain variants, considered as intermediate cases in degrees 9 and 10, which we call 2-Orientation and 2-Spin structures, respectively. As in the lower degree cases, we also discuss the natural twists of these structures and characterize the corresponding topological groups associated to each of the structures, which likewise admit refinements to differential cohomology.

scholarly journals Cosmological implications of spectator and dynamical fields during inflation

2020 ◽  
Author(s):  
◽  
Jonathan Holland
Keyword(s):  
Vector Field ◽  
String Theory ◽  
Gauge Field ◽  
Gauge Fields ◽  
Next Generation ◽  
Single Field ◽  
Inflationary Models

Some possible cosmological implications of the inclusion of spectator gauge fields in the inflationary action are considered. In this context, a spec-tator field is a field that is not directly responsible for inflation but can affect cosmological observables. Spectator gauge fields can lead to novel and distinguishable features in inflationary models (as compared to single-field inflation) that may be detectable. A model of anisotropic inflation is considered where universal anisotropy is maintained through a vector field that is coupled to both the inflaton and its derivative. The derivative cou-pling reduces the anisotropy induced when compared to the non-derivative case, reducing tension with observations. SU(N) gauge fields appear natu-rally in the actions of string inflation models. The inclusion of an SU(N) gauge field coupled both to scalars and pseudo-scalars (axions) is considered in two models of string inflation whose inflatons are K¨ahler moduli: K¨ahler moduli inflation and fibre inflation. It is shown that the coupling between the axion and the gauge field can lead to a large (chiral) enhancement of the tensor spectrum of these two models. In the case of K¨ahler moduli inflation, a model that generically predicts an unobservable value for the tensor-to-scalar ratio (r  10−3), this enhancement is capable of boost-ing the tensor-to-scalar ratio to values that will be potentially observable at next generation detectors. However, the parameters required to achieve this goal may present a challenge for its successful realisation in string theory. In the case of fibre inflation, a model that generically predicts an observable value for the tensor-to-scalar ratio, it is shown that this enhancement can render the tensor spectrum of fibre inflation almost entirely chiral, giving it a distinguishable feature that may be detectable.

scholarly journals Construction of inflationary scenarios with the Gauss–Bonnet term and nonminimal coupling

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Ekaterina O. Pozdeeva ◽  
Sergey Yu. Vernov
Keyword(s):  
Scalar Field ◽  
Spectral Index ◽  
Effective Potential ◽  
Ricci Scalar ◽  
Nonminimal Coupling ◽  
Scalar Spectral Index ◽  
Bonnet Term ◽  
Inflationary Models ◽  
Scalar Perturbations ◽  
The Way

AbstractInflationary models with a scalar field nonminimally coupled both with the Ricci scalar and with the Gauss–Bonnet term are studied. We propose the way of generalization of inflationary scenarios with the Gauss–Bonnet term and a scalar field minimally coupled with the Ricci scalar to the corresponding scenarios with a scalar field nonminimally coupled with the Ricci scalar. Using the effective potential, we construct a set of models with the same values of the scalar spectral index $$n_s$$ n s and the amplitude of the scalar perturbations $$A_s$$ A s and different values of the tensor-to-scalar ratio r.

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