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 Suppression of the Primordial Gravitational Waves

2016 ◽  
Vol 43 ◽  
pp. 1660204 ◽  
Author(s):  
Gansukh Tumurtushaa ◽  
Seoktae Koh ◽  
Bum-Hoon Lee
Keyword(s):  
Phase Transition ◽  
Energy Spectrum ◽  
Gravitational Waves ◽  
Low Frequency ◽  
Frequency Range ◽  
Model Parameter ◽  
Evolution Of The Universe ◽  
Inflation Model ◽  
Primordial Gravitational Waves ◽  
The Universe

We study the primordial gravitational waves induced by space-space condensate inflation model. For modes that cross the comoving horizon during matter dominated era, we calculate the energy spectrum of gravitational waves. The energy spectrum of gravitational waves for our model has significantly suppressed in the low frequency range. The suppression occurs due to the phase transition during the early evolution of the Universe and depends on model parameter.

scholarly journals Primordial monopoles and strings, inflation, and gravity waves

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Joydeep Chakrabortty ◽  
George Lazarides ◽  
Rinku Maji ◽  
Qaisar Shafi
Keyword(s):  
Symmetry Breaking ◽  
Gravity Waves ◽  
Cosmic Strings ◽  
Wave Spectrum ◽  
Gauge Coupling ◽  
String Tension ◽  
Magnetic Monopoles ◽  
Intermediate Scale ◽  
Tension Parameter ◽  
The Universe

Abstract We consider magnetic monopoles and strings that appear in non-supersymmetric SO(10) and E6 grand unified models paying attention to gauge coupling unification and proton decay in a variety of symmetry breaking schemes. The dimensionless string tension parameter Gμ spans the range 10−6− 10−30, where G is Newton’s constant and μ is the string tension. We show how intermediate scale monopoles with mass ∼ 1013− 1014 GeV and flux ≲ 2.8 × 10−16 cm−2s−1sr−1, and cosmic strings with Gμ ∼ 10−11− 10−10 survive inflation and are present in the universe at an observable level. We estimate the gravity wave spectrum emitted from cosmic strings taking into account inflation driven by a Coleman-Weinberg potential. The tensor-to-scalar ratio r lies between 0.06 and 0.003 depending on the details of the inflationary scenario.

The Effect of Pitch Gyradius on Added Resistance of Yacht Hulls

1991 ◽  
Author(s):  
James F. Moran
Keyword(s):  
Water Resistance ◽  
Wave Spectrum ◽  
Response Amplitude ◽  
Added Resistance ◽  
Regular Waves ◽  
Low Frequencies ◽  
Irregular Wave ◽  
Wave Data ◽  
The Difference ◽  
Response Amplitude Operators

The purpose of this investigation was to determine the effect of pitch gyradius on added resistance of yacht hulls. Tank testing of a model yacht in head seas was performed in the Webb Robinson Model Basin. The model was tested in regular waves at two speeds and five variations of gyradius. The model was also evaluated in irregular seas of the Pierson-Moskowitz spectrum at various speeds with two gyradii. Response Amplitude Operators were developed from the regular wave data and comparisons made. The irregular wave data were analyzed for the effect of speed on the difference in added resistance between the maximum and minimum gyradius settings. Several conclusions were arrived at after analyzing the data. The Response Amplitude Operaters shift as the gyradius changes. In regular waves, at low frequencies of encounter, a lower, gyradius resulted in less added frequencies of encounter in regular waves, this trend reverses itself and the higher gyradii result in reduced added resistance. However, at higher frequencies of encounter in regular waves, this trend reverses, reverses itself in reduced added resistance. The peaks of the RAO curves shift to higher frequencies at higher gyradii. It was also concluded that at the higher speed, Froude Number of 0.3, the added resistance was lower relative to the still-water resistance for each gyradius tested. The irregular wave testing revealed the effect of the lower frequencies dominating the irregular wave spectrum. The minimum gyradius, in irregular seas showed less added resistance than the maximum gyradius. In addition, the irregular wave testing verified, the reduction of added resistance, relative to still-water resistance, at increasing speeds for both the minimum and maximum gyradii.

COMMENT ON "ANGULAR SIZE TEST ON THE EXPANSION OF THE UNIVERSE," BY M. LÓPEZ-CORREDOIRA

2011 ◽  
Vol 20 (06) ◽  
pp. 1167-1169 ◽  
Author(s):  
D. L. KHOKHLOV
Keyword(s):  
Angular Size ◽  
Radio Sources ◽  
Expansion Of The Universe ◽  
The Difference ◽  
The Universe

The results of the angular size test in the paper under comment are at variance with those for compact radio sources. The possible reason for the difference between the two results is discussed.

Gamma-Ray Bursts as Probes of the Universe

2011 ◽  
Author(s):  
Joshua S. Bloom
Keyword(s):  
Star Formation ◽  
Cosmic Rays ◽  
Gravitational Waves ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Ongoing Study ◽  
Observable Universe ◽  
History Of ◽  
Expansion Of The Universe ◽  
The Universe

This chapter focuses on how gamma-ray bursts (GRBs) are emerging as unique tools in the study of broad areas of astronomy and physics by virtue of their special properties. The unassailable fact about GRBs that makes them such great probes is that they are fantastically bright and so can be seen to the farthest reaches of the observable Universe. In parallel with the ongoing study of GRB events and progenitors, new lines of inquiry have burgeoned: using GRBs as unique probes of the Universe in ways that are almost completely divorced from the nature of GRBs themselves. Topics discussed include studies of gas, dust, and galaxies; the history of star formation; measuring reionization and the first objects in the universe; neutrinos, gravitational waves, and cosmic rays; quantum gravity and the expansion of the universe; and the future of GRBs.

scholarly journals Magnetism in the Early Universe

2018 ◽  
Vol 14 (A30) ◽  
pp. 295-298
Author(s):  
Tina Kahniashvili ◽  
Axel Brandenburg ◽  
Arthur Kosowsky ◽  
Sayan Mandal ◽  
Alberto Roper Pol
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Gravitational Waves ◽  
Early Universe ◽  
Large Scale ◽  
Direct Detection ◽  
Correlation Lengths ◽  
Cosmological Scenario ◽  
Expansion Of The Universe ◽  
The Universe

AbstractBlazar observations point toward the possible presence of magnetic fields over intergalactic scales of the order of up to ∼1 Mpc, with strengths of at least ∼10−16 G. Understanding the origin of these large-scale magnetic fields is a challenge for modern astrophysics. Here we discuss the cosmological scenario, focussing on the following questions: (i) How and when was this magnetic field generated? (ii) How does it evolve during the expansion of the universe? (iii) Are the amplitude and statistical properties of this field such that they can explain the strengths and correlation lengths of observed magnetic fields? We also discuss the possibility of observing primordial turbulence through direct detection of stochastic gravitational waves in the mHz range accessible to LISA.

scholarly journals On the non-linear energy transfer in a gravity-wave spectrum. Part 3. Evaluation of the energy flux and swell-sea interaction for a Neumann spectrum

1963 ◽  
Vol 15 (3) ◽  
pp. 385-398 ◽  
Author(s):  
K. Hasselmann
Keyword(s):  
Energy Transfer ◽  
Gravity Wave ◽  
Wave Spectrum ◽  
Low Frequency ◽  
Low Frequencies ◽  
Frequency Peak ◽  
Non Linear ◽  
Gain Energy ◽  
Rate Of Decay ◽  
Linear Interactions

The energy transfer due to non-linear interactions between the components of a gravity-wave spectrum discussed in Parts 1 and 2 of this paper is evaluated for a fully and partially developed Neumann spectrum with various spreading factors. The characteristic time scales of the energy transfer are found to be typically of the order of a few hours. In all cases the high frequencies and the low-frequency peak are found to gain energy from an intermediate range of frequencies. The transfer of energy to very low frequencies and to waves travelling at large angles to the main propagation direction of the spectrum is negligible. Computations are presented also for the rate of decay of swell interacting with local wind-generated seas (represented by a Neumann spectrum). An appreciable decay is found only for swell frequencies in the same range as those of the local sea.

scholarly journals BARYOGENESIS VIA DENSITY FLUCTUATIONS WITH A SECOND ORDER ELECTROWEAK PHASE TRANSITION

2003 ◽  
Vol 18 (26) ◽  
pp. 4851-4868 ◽  
Author(s):  
BISWANATH LAYEK ◽  
SOMA SANYAL ◽  
AJIT M. SRIVASTAVA
Keyword(s):  
Phase Transition ◽  
Baryon Asymmetry ◽  
Density Fluctuations ◽  
Second Order ◽  
Baryon Production ◽  
Electroweak Phase Transition ◽  
Expansion Of The Universe ◽  
Second Order Transition ◽  
Background Temperature ◽  
The Universe

We consider the presence of cosmic string induced density fluctuations in the universe at temperatures below the electroweak phase transition temperature. Resulting temperature fluctuations can restore the electroweak symmetry locally, depending on the amplitude of fluctuations and the background temperature. The symmetry will be spontaneously broken again in a given fluctuation region as the temperature drops there (for fluctuations with length scales smaller than the horizon), resulting in the production of baryon asymmetry. The time scale of the transition will be governed by the wavelength of fluctuation and, hence, can be much smaller than the Hubble time. This leads to strong enhancement in the production of baryon asymmetry for a second order electroweak phase transition as compared to the case when transition happens due to the cooling of the universe via expansion. For a two-Higgs extension of the Standard Model (with appropriate CP violation), we show that one can get the required baryon to entropy ratio if fluctuations propagate without getting significantly damped. If fluctuations are damped rapidly, then a volume factor suppresses the baryon production. Still, the short scale of the fluctuation leads to enhancement of the baryon to entropy ratio by at least 3–4 orders of magnitude compared to the conventional case of second order transition where the cooling happens due to expansion of the universe.

scholarly journals QUANTUM CREATION OF A TOPOLOGICAL BLACK HOLE

2000 ◽  
Vol 15 (25) ◽  
pp. 1589-1595 ◽  
Author(s):  
ZHONG CHAO WU
Keyword(s):  
Phase Transition ◽  
Black Hole ◽  
De Sitter ◽  
Sitter Background ◽  
The Difference ◽  
The Universe

The constrained instanton method is used to study quantum creation of a vacuum or charged topological black hole. At the WKB level, the relative creation probability is the exponential of a quarter of the sum of the horizon areas associated with the seed instanton. The universe without a black hole has the highest creation probability. The difference between this creation scenario and the Hawking–Page phase transition in the anti-de Sitter background is clarified.

Pulsar timing and relativistic gravity

1992 ◽  
Vol 341 (1660) ◽  
pp. 117-134 ◽  
Keyword(s):  
Gravitational Waves ◽  
Binary Systems ◽  
Strong Field ◽  
Low Frequency ◽  
Rate Of Change ◽  
Pulsar Timing ◽  
Basic Physics ◽  
Time Standards ◽  
The Universe

In addition to being fascinating objects to study in their own right, pulsars are exquisite tools for probing a variety of issues in basic physics. Recycled pulsars, thought to have been spun up in previous episodes of mass accretion from orbiting companion stars, are especially well suited for such applications. They are extraordinarily stable clocks, approaching and perhaps exceeding the long-term stabilities of the best terrestrial time standards. Most of them are found in binary systems, with orbital velocities as large as 10 -3 c. They provide unique opportunities for measuring neutron star masses, thereby yielding fundamental astrophysical data difficult to acquire by any other means. And they open the way for high precision tests of the nature of gravity under conditions much more ‘relativistic ’ than found anywhere within the Solar System. Among other results, pulsar timing observations have convincingly established the existence of quadrupolar gravitational waves propagating at the speed of light. They have also placed interesting limits on possible departures of the strong-field nature of gravity from general relativity, on the rate of change of Newton’s constant, G , and on the energy density of low-frequency gravitational waves in the universe.

Sign in / Sign up

Export Citation Format

Share Document