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We introduce the real space correlation function of $B$-mode polarization of the cosmic microwave background (CMB) as a probe of superhorizon tensor perturbations created by inflation. By causality, any non-inflationary mechanism for…

Cosmology and Nongalactic Astrophysics · Physics 2010-01-15 Daniel Baumann , Matias Zaldarriaga

Cosmological phase transitions in the primordial universe can produce anisotropic stochastic gravitational wave backgrounds (GWB), similar to the cosmic microwave background (CMB). For adiabatic perturbations, the fluctuations in GWB follow…

Cosmology and Nongalactic Astrophysics · Physics 2021-12-01 Soubhik Kumar , Raman Sundrum , Yuhsin Tsai

One of the most promising ways of detecting primordial gravitational waves generated during inflation is to observe B-modes of polarization, generated by Thomson scattering after reionization, in the cosmic microwave background (CMB). Large…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-20 Scott Dodelson

We present a follow-up study to the method recently proposed by Namikawa and Sherwin (2023) to probe gravitational waves using cross-correlations between two cosmic microwave background (CMB) $B$-modes and a large-scale structure tracer. We…

Cosmology and Nongalactic Astrophysics · Physics 2025-09-29 Toshiya Namikawa , Irene Abril-Cabezas , Blake D. Sherwin

The anisotropy study cosmic microwave background (CMB) is one of the main observational tools for modern cosmology. However, alongside the study of the thermal fluctuations of the CMB are other equally important information, which is known…

Cosmology and Nongalactic Astrophysics · Physics 2016-01-18 Alexander Bonilla Rivera

The nonlinear interaction between one graviton and two scalars is enhanced in specific inflationary models, potentially leading to distinguishable signatures in the bispectrum of the cosmic microwave background (CMB) anisotropies. We…

Cosmology and Nongalactic Astrophysics · Physics 2018-01-15 Maresuke Shiraishi , Michele Liguori , James R. Fergusson

We present a Gaussianity test of the cosmic microwave background (CMB) polarization by analyzing the statistics of unpolarized points in the sky, classified into three distinct types: saddles, comets, and beaks. This classification of…

Cosmology and Nongalactic Astrophysics · Physics 2025-12-01 K. O. Parfenov , D. I. Novikov , A. O. Mihalchenko

We review the prospects for detecting tensor modes generated during inflation by CMB polarization experiments and by searching for a stochastic gravitational wave background with laser interferometers in space. We tackle the following two…

Astrophysics · Physics 2009-11-11 George Efstathiou , Sirichai Chongchitnan

The presence of non--Gaussian features in the Cosmic Microwave Background (CMB) radiation maps represents one of the most long--awaited clues in the search for the actual structure of the primordial radiation, still needing confirmation.…

Astrophysics · Physics 2009-10-22 Alejandro Gangui

The measurements of the statistical properties of the Cosmic Microwave Background (CMB) fluctuations enable us to probe the physics of the very early Universe especially at the epoch of inflation. A particular interest lays on the detection…

Cosmology and Nongalactic Astrophysics · Physics 2011-06-07 S. Pires , S. Plaszczynski , A. Lavabre

In this work we analyse in detail the possibility of using small and intermediate-scale gravitational wave anisotropies to constrain the inflationary particle content. First, we develop a phenomenological approach focusing on anisotropies…

Cosmology and Nongalactic Astrophysics · Physics 2022-03-09 Ema Dimastrogiovanni , Matteo Fasiello , Ameek Malhotra , P. Daniel Meerburg , Giorgio Orlando

The inflationary $B$-mode signals encode invaluable information about the origin of our Universe and searching for potential signatures of primordial gravitational waves (PGWs) is one of the major science goals for future precision…

Cosmology and Nongalactic Astrophysics · Physics 2025-12-09 Sen Li , Chang Feng , Filipe B. Abdalla

A primordial cosmic microwave background B-mode is widely considered a "smoking gun" signature of an early period of inflationary expansion. However, competing theories of the origin of structure, including string gases and bouncing…

Cosmology and Nongalactic Astrophysics · Physics 2019-04-11 Brian A. Powell

Recent theoretical results indicate that the detection of primordial gravity waves from inflation may be a hopeless task. First, foregrounds from lensing put a strict lower limit on the detectability of the B-mode polarization signal in the…

Astrophysics · Physics 2015-06-24 William H. Kinney

A detection of the primordial gravitational wave background is considered to be the ``smoking-gun '' evidence for inflation. While super-horizon waves are probed with cosmic microwave background (CMB) polarization, the relic background will…

Astrophysics · Physics 2011-05-12 Tristan L. Smith , Hiranya V. Peiris , Asantha Cooray

Inflationary cosmology is successful in explaining a number of outstanding cosmological issues including the flatness, the horizon and the relic issues. More spectacular is the experimental confirmation of the structure as arose from the…

General Relativity and Quantum Cosmology · Physics 2010-02-17 Wei-Tou Ni

It is well known that non-trivial squeezed tensor bispectra can lead to anisotropies in the inflationary stochastic gravitational wave (GW) background, providing us with an alternative and complementary window to primordial…

Cosmology and Nongalactic Astrophysics · Physics 2022-12-14 Giorgio Orlando

Primordial gravitational waves could be non-Gaussian, just like primordial scalar perturbations. Although the tensor two-point function has thus-far remained elusive, the three-point function could, in principle, be large enough to be…

Cosmology and Nongalactic Astrophysics · Physics 2025-05-14 Oliver H. E. Philcox , Maresuke Shiraishi

Recent second-order perturbation computations have provided an accurate prediction for the primordial gravitational potential $\Phi(x)$ in scenarios in which cosmological perturbations are generated either during or after inflation. This…

Astrophysics · Physics 2008-11-26 M. Liguori , F. K. Hansen , E. Komatsu , S. Matarrese , A. Riotto

In addition to density perturbations, inflationary models of the early universe generally predict a stochastic background of gravitational waves or tensor fluctuations. By making use of the inflationary flow approach for single field models…

Astrophysics · Physics 2008-11-26 Brett C. Friedman , Asantha Cooray , Alessandro Melchiorri