scholarly journals Polarized Initial States of Primordial Gravitational Waves

Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 672
Author(s):  
Sugumi Kanno ◽  
Jiro Soda
Keyword(s):  
Gravitational Waves ◽  
Modified Gravity ◽  
Coherent States ◽  
Inflationary Universe ◽  
Dynamical Generation ◽  
Primordial Gravitational Waves ◽  
Initial States ◽  
Matter Fields

Polarizations of primordial gravitational waves can be relevant when considering an inflationary universe in modified gravity or when matter fields survive during inflation. Such polarizations have been discussed in the Bunch–Davies vacuum. Instead of taking into account the dynamical generation of polarizations of gravitational waves, in this paper, we consider polarized initial states constructed from S U ( 2 ) coherent states. We then evaluate the power spectrums of the primordial gravitational waves in the states.

scholarly journals Resonance instability of primordial gravitational waves during inflation in Chern–Simons gravity

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
Chengjie Fu ◽  
Jing Liu ◽  
Tao Zhu ◽  
Hongwei Yu ◽  
Puxun Wu
Keyword(s):  
Energy Spectrum ◽  
Periodic Function ◽  
Gravitational Waves ◽  
Infrared Region ◽  
Einstein Gravity ◽  
Model Parameters ◽  
Primordial Gravitational Waves ◽  
Chern Simons ◽  
Matter Fields ◽  
Sharp Cutoff

AbstractWe investigate axion inflation where the gravitational Chern–Simons term is coupled to a periodic function of the inflaton. We find that tensor perturbations with different polarizations are amplified in different ways by the Chern–Simons coupling. Depending on the model parameters, the resonance amplification results in a parity-violating peak or a board plateau in the energy spectrum of gravitational waves, and the sharp cutoff in the infrared region constitutes a characteristic distinguishable from stochastic gravitational wave backgrounds produced by matter fields in Einstein gravity.

scholarly journals Probing primordial gravitational waves: Ali CMB Polarization Telescope

2018 ◽  
Vol 6 (1) ◽  
pp. 145-154 ◽  
Author(s):  
Hong Li ◽  
Si-Yu Li ◽  
Yang Liu ◽  
Yong-Ping Li ◽  
Yifu Cai ◽  
...  
Keyword(s):  
Gravitational Waves ◽  
High Energy Physics ◽  
Transition Edge Sensor ◽  
High Energy ◽  
Cpt Symmetry ◽  
Joint Project ◽  
Current Limit ◽  
Scientific Goal ◽  
Primordial Gravitational Waves ◽  
Cmb Polarization

Abstract In this paper, we will give a general introduction to the Ali CMB Polarization Telescope (AliCPT) project, which is a Sino–US joint project led by the Institute of High Energy Physics and involves many different institutes in China. It is the first ground-based Cosmic Microwave Background (CMB) polarization experiment in China and an integral part of China's Gravitational-wave Program. The main scientific goal of the AliCPT project is to probe the primordial gravitational waves (PGWs) originating from the very early Universe. The AliCPT project includes two stages. The first stage, referred to as AliCPT-1, is to build a telescope in the Ali region of Tibet at an altitude of 5250 meters. Once completed, it will be the highest ground-based CMB observatory in the world and will open a new window for probing PGWs in the northern hemisphere. The AliCPT-1 telescope is designed to have about 7000 transition-edge sensor detectors at 95 GHz and 150 GHz. The second stage is to have a more sensitive telescope (AliCPT-2) with more than 20 000 detectors. Our simulations show that AliCPT will improve the current constraint on the tensor-to-scalar ratio r by one order of magnitude with three years' observation. Besides the PGWs, AliCPT will also enable a precise measurement of the CMB rotation angle and provide a precise test of the CPT symmetry. We show that three years' observation will improve the current limit by two orders of magnitude.

scholarly journals New constraints on primordial gravitational waves from Planck 2015

2016 ◽  
Vol 760 ◽  
pp. 823-825 ◽  
Author(s):  
Luca Pagano ◽  
Laura Salvati ◽  
Alessandro Melchiorri
Keyword(s):  
Gravitational Waves ◽  
Primordial Gravitational Waves
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