scholarly journals Gravity waves as a probe of the Hubble expansion rate during an electroweak scale phase transition

2010 ◽  
Vol 82 (2) ◽  
Author(s):  
Daniel J. H. Chung ◽  
Peng Zhou
Keyword(s):  
Phase Transition ◽  
Gravity Waves ◽  
Expansion Rate ◽  
Electroweak Scale ◽  
Hubble Expansion

scholarly journals Do supernovae indicate an accelerating universe?

2021 ◽  
Author(s):  
Roya Mohayaee ◽  
Mohamed Rameez ◽  
Subir Sarkar
Keyword(s):  
Dark Energy ◽  
Large Scale ◽  
Bulk Flow ◽  
Expansion Rate ◽  
Accelerated Expansion ◽  
Accelerating Universe ◽  
Acoustic Oscillations ◽  
Independent Evidence ◽  
Peculiar Velocity ◽  
Hubble Expansion

AbstractIn the late 1990’s, observations of two directionally-skewed samples of, in total, 93 Type Ia supernovae were analysed in the framework of the Friedmann–Lemaître–Robertson–Walker (FLRW) cosmology. Assuming these to be ‘standard(isable) candles’ it was inferred that the Hubble expansion rate is accelerating as if driven by a positive Cosmological Constant $$\varLambda $$ Λ in Einstein’s theory of gravity. This is still the only direct evidence for the ‘dark energy’ that is the dominant component of today’s standard $$\varLambda $$ Λ CDM cosmological model. Other data such as baryon acoustic oscillations (BAO) in the large-scale distribution of galaxies, temperature fluctuations in the cosmic microwave background (CMB), measurement of stellar ages, the rate of growth of structure, etc are all ‘concordant’ with this model but do not provide independent evidence for accelerated expansion. The recent discussions about whether the inferred acceleration is real rests on analysis of a larger sample of 740 SNe Ia which shows that these are not quite standard candles, and more importantly highlights the ‘corrections’ that are applied to analyse the data in the FLRW framework. The latter holds in the reference frame in which the CMB is isotropic, whereas observations are carried out in our heliocentric frame in which the CMB has a large dipole anisotropy. This is assumed to be of kinematic origin i.e. due to our non-Hubble motion driven by local inhomogeneity in the matter distribution which has grown under gravity from primordial density perturbations traced by the CMB fluctuations. The $$\varLambda $$ Λ CDM model predicts how this peculiar velocity should fall off as the averaging scale is raised and the universe becomes sensibly homogeneous. However observations of the local ‘bulk flow’ are inconsistent with this expectation and convergence to the CMB frame is not seen. Moreover, the kinematic interpretation implies a corresponding dipole in the sky distribution of high redshift quasars, which is rejected by observations at $$4.9\sigma $$ 4.9 σ . Hence the peculiar velocity corrections employed in supernova cosmology are inconsistent and discontinuous within the data. The acceleration of the Hubble expansion rate is in fact anisotropic at $$3.9\sigma $$ 3.9 σ and aligned with the bulk flow. Thus dark energy could be an artefact of analysing data assuming that we are idealised observers in an FLRW universe, when in fact the real universe is inhomogeneous and anisotropic out to distances large enough to impact on cosmological analyses.

scholarly journals Dark Matter Around the Local Group?

1988 ◽  
Vol 130 ◽  
pp. 585-585
Author(s):  
Edmond Giraud
Keyword(s):  
Dark Matter ◽  
Velocity Field ◽  
Velocity Distribution ◽  
Local Group ◽  
Spiral Galaxies ◽  
Small Distance ◽  
Expansion Rate ◽  
Fall Velocity ◽  
Hubble Expansion ◽  
Local Value

The Hubble expansion rate measured in the short distance scale varies from 70–75 to 90 km s−1 Mpc−1 as the kinematic distance (corrected for in fall velocity toward Virgo) increases from Dv = 200–400 km s−1 to Dv ∼ 1300 km s−1. It should be observed in the long scale as well (starting from a lower value), if the same methods were used in the same way. The Malmquist bias for spiral galaxies in the range Dv ≤ 1300 km s−1 is very small or null. The velocity distribution of galaxies in the nearest groups compared with models of various rms velocity dispersions, suggests that at small distance, dispersions of 100 km s−1 or more do not fit the observations. The effect of the deceleration due to the mass of the Local Group on the very nearby velocity field is negligible beyond 2.5–3 Mpc. The low local value of Ho extends approximately over ∼ 6–7 Mpc.

scholarly journals Baryogenesis and gravity waves from a UV-completed electroweak phase transition

2021 ◽  
Vol 103 (12) ◽  
Author(s):  
Benoit Laurent ◽  
James M. Cline ◽  
Avi Friedlander ◽  
Dong-Ming He ◽  
Kimmo Kainulainen ◽  
...  
Keyword(s):  
Phase Transition ◽  
Gravity Waves ◽  
Electroweak Phase Transition

scholarly journals Gravitational tests of electroweak relaxation

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Daniele Barducci ◽  
Enrico Bertuzzo ◽  
Martín Arteaga Tupia
Keyword(s):  
Phase Transition ◽  
Strong Interactions ◽  
Back Reaction ◽  
Electroweak Scale ◽  
First Order ◽  
Relaxation Phase ◽  
First Order Phase Transition ◽  
Reaction Potential ◽  
First Order Phase ◽  
The Universe

Abstract We consider a scenario in which the electroweak scale is stabilized via the relaxion mechanism during inflation, focussing on the case in which the back-reaction potential is generated by the confinement of new strongly interacting vector-like fermions. If the reheating temperature is sufficiently high to cause the deconfinement of the new strong interactions, the back-reaction barrier then disappears and the Universe undergoes a second relaxation phase. This phase stops when the temperature drops sufficiently for the back-reaction to form again. We identify the regions of parameter space in which the second relaxation phase does not spoil the successful stabilization of the electroweak scale. In addition, the generation of the back-reaction potential that ends the second relaxation phase can be associated to a strong first order phase transition. We then study when such transition can generate a gravitational wave signal in the range of detectability of future interferometer experiments.

scholarly journals Hubble inflation in Randall–Sundrum type II model

2020 ◽  
Vol 29 (06) ◽  
pp. 2050037
Author(s):  
Habib Abedi ◽  
Amir M. Abbassi ◽  
Sebastian Bahamonde
Keyword(s):  
Field Model ◽  
High Energy ◽  
Expansion Rate ◽  
Type Ii ◽  
Flow Equations ◽  
Hubble Expansion ◽  
Jacobi Formalism ◽  
Inflationary Parameters ◽  
High Energy Regime ◽  
Model Features

We study a braneworld Randall–Sundrum type II (RSII) model using the Hamilton–Jacobi formalism. We extend the standard inflationary parameters and the flow equations for this braneworld scenario. We investigate the conditions that reduce the infinite number of flow equations into a finite number and confirm that by considering one of the inflationary parameters that vanishes, the Hubble expansion rate gets a polynomial form in both General Relativity (GR) and in the high-energy regime of RSII. We also show that if one sets this inflationary parameter to a constant value, the model features a nonpolynomial form of the Hubble expansion rate. The form of the Hubble parameter in this case is different in GR and RSII. Next, we consider a single-scalar field model with a Hubble expansion rate behaving as [Formula: see text] and show that compared to GR, the RSII model has a smaller tensor-to-scalar ratio and larger spectral index for [Formula: see text]. Therefore, RSII model leads to better predictions than GR.

scholarly journals Gravity waves from a cosmological phase transition: Gauge artifacts and daisy resummations

2011 ◽  
Vol 84 (2) ◽  
Author(s):  
Carroll Wainwright ◽  
Stefano Profumo ◽  
Michael J. Ramsey-Musolf
Keyword(s):  
Phase Transition ◽  
Gravity Waves

scholarly journals Causal gravitational waves as a probe of free streaming particles and the expansion of the Universe

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Anson Hook ◽  
Gustavo Marques-Tavares ◽  
Davide Racco
Keyword(s):  
Phase Transition ◽  
Gravitational Waves ◽  
Gravity Waves ◽  
Wave Spectrum ◽  
Spectral Feature ◽  
Low Frequency ◽  
Low Frequencies ◽  
Expansion Of The Universe ◽  
The Difference ◽  
The Universe

Abstract The low frequency part of the gravitational wave spectrum generated by local physics, such as a phase transition or parametric resonance, is largely fixed by causality, offering a clean window into the early Universe. In this work, this low frequency end of the spectrum is analyzed with an emphasis on a physical understanding, such as the suppressed production of gravitational waves due to the excitation of an over-damped harmonic oscillator and their enhancement due to being frozen out while outside the horizon. Due to the difference between sub-horizon and super-horizon physics, it is inevitable that there will be a distinct spectral feature that could allow for the direct measurement of the conformal Hubble rate at which the phase transition occurred. As an example, free-streaming particles (such as the gravity waves themselves) present during the phase transition affect the production of super-horizon modes. This leads to a steeper decrease in the spectrum at low frequencies as compared to the well-known causal k3 super-horizon scaling of stochastic gravity waves. If a sizable fraction of the energy density is in free-streaming particles, they even lead to the appearance of oscillatory features in the spectrum. If the universe was not radiation dominated when the waves were generated, a similar feature also occurs at the transition between sub-horizon to super-horizon causality. These features are used to show surprising consequences, such as the fact that a period of matter domination following the production of gravity waves actually increases their power spectrum at low frequencies.

scholarly journals COSMIC SCALAR FIELDS WITH FLAT POTENTIAL

2002 ◽  
Vol 17 (21) ◽  
pp. 1383-1391 ◽  
Author(s):  
J. W. van HOLTEN
Keyword(s):  
Phase Transition ◽  
Simple Model ◽  
Scalar Fields ◽  
Expansion Rate ◽  
The Universe

The dynamics of cosmic scalar fields with flat potential is studied. Their contribution to the expansion rate of the universe is analyzed, and their behavior in a simple model of phase transition is discussed.

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