Introductory Chapter: Black Holes, The Singularity Problem, and The Universe

General relativity explains much more than the spacetime around static spherical masses.We briefly assess general relativity in the larger context of physical theories, then explore various general relativistic effects that have no Newtonian analog. First, source massmotion gives rise to gravitomagnetic effects on test particles.These effects also depend on the velocity of the test particle, which has substantial implications for orbits around black holes to be further explored in Chapter 20. Second, any changes in the sourcemass ripple outward as gravitational waves, and we tell the century‐long story from the prediction of gravitational waves to their first direct detection in 2015. Third, the deflection of light by galaxies and clusters of galaxies allows us to map the amount and distribution of mass in the universe in astonishing detail. Finally, general relativity enables modeling the universe as a whole, and we explore the resulting Big Bang cosmology.

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Black Holes in the Universe

Highlights of Astronomy ◽

10.1017/s1539299600019936 ◽

1998 ◽

Vol 11 (1) ◽

pp. 28-41

Author(s):

I.D. Novikov

Keyword(s):

Black Holes ◽

Black Hole ◽

Neutron Stars ◽

Supernova Explosions ◽

The Universe

Some 30 years ago very few scientists thought that black holes may really exist. Attention focussed on the black hole hypothesis after neutron stars had been discovered. It was rather surprising that astrophysicists immediately ‘welcomed’ black holes. They found their place not only in the remnants of supernova explosions but also in the nuclei of galaxies and quasars.

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A Tale of Two Infinities

10.1093/oso/9780192898159.001.0001 ◽

2021 ◽

Author(s):

Gianfranco Bertone

Keyword(s):

Black Holes ◽

Dark Matter ◽

Gravitational Waves ◽

Direct Detection ◽

Traditional Approach ◽

Fundamental Physics ◽

Modern Cosmology ◽

Nobel Prize In Physics ◽

The Universe ◽

Modern Astronomy

The spectacular advances of modern astronomy have opened our horizon on an unexpected cosmos: a dark, mysterious Universe, populated by enigmatic entities we know very little about, like black holes, or nothing at all, like dark matter and dark energy. In this book, I discuss how the rise of a new discipline dubbed multimessenger astronomy is bringing about a revolution in our understanding of the cosmos, by combining the traditional approach based on the observation of light from celestial objects, with a new one based on other ‘messengers’—such as gravitational waves, neutrinos, and cosmic rays—that carry information from otherwise inaccessible corners of the Universe. Much has been written about the extraordinary potential of this new discipline, since the 2017 Nobel Prize in physics was awarded for the direct detection of gravitational waves. But here I will take a different angle and explore how gravitational waves and other messengers might help us break the stalemate that has been plaguing fundamental physics for four decades, and to consolidate the foundations of modern cosmology.

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Symmetry and the Arrow of Time in Theoretical Black Hole Astrophysics

Journal of Gravity ◽

10.1155/2015/530850 ◽

2015 ◽

Vol 2015 ◽

pp. 1-5

Author(s):

David Garofalo

Keyword(s):

Black Holes ◽

Black Hole ◽

Active Galactic Nuclei ◽

Accretion Disks ◽

Time Reversal ◽

Large Scale ◽

Galactic Nuclei ◽

Arrow Of Time ◽

Time Symmetry ◽

The Universe

While the basic laws of physics seem time-reversal invariant, our understanding of the apparent irreversibility of the macroscopic world is well grounded in the notion of entropy. Because astrophysics deals with the largest structures in the Universe, one expects evidence there for the most pronounced entropic arrow of time. However, in recent theoretical astrophysics work it appears possible to identify constructs with time-reversal symmetry, which is puzzling in the large-scale realm especially because it involves the engines of powerful outflows in active galactic nuclei which deal with macroscopic constituents such as accretion disks, magnetic fields, and black holes. Nonetheless, the underlying theoretical structure from which this accreting black hole framework emerges displays a time-symmetric harmonic behavior, a feature reminiscent of basic and simple laws of physics. While we may expect such behavior for classical black holes due to their simplicity, manifestations of such symmetry on the scale of galaxies, instead, surprise. In fact, we identify a parallel between the astrophysical tug-of-war between accretion disks and jets in this model and the time symmetry-breaking of a simple overdamped harmonic oscillator. The validity of these theoretical ideas in combination with this unexpected parallel suggests that black holes are more influential in astrophysics than currently recognized and that black hole astrophysics is a more fundamental discipline.

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Primordial black holes from the QCD epoch: linking dark matter, baryogenesis, and anthropic selection

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3726 ◽

2020 ◽

Vol 501 (1) ◽

pp. 1426-1439

Author(s):

Bernard Carr ◽

Sebastien Clesse ◽

Juan García-Bellido

Keyword(s):

Black Holes ◽

Dark Matter ◽

Selection Effect ◽

Mass Function ◽

Baryon Asymmetry ◽

Primordial Black Holes ◽

Cosmological Horizon ◽

Chandrasekhar Limit ◽

The Universe ◽

Characteristic Mass

ABSTRACT If primordial black holes (PBHs) formed at the quark-hadron epoch, their mass must be close to the Chandrasekhar limit, this also being the characteristic mass of stars. If they provide the dark matter (DM), the collapse fraction must be of order the cosmological baryon-to-photon ratio ∼10−9, which suggests a scenario in which a baryon asymmetry is produced efficiently in the outgoing shock around each PBH and then propagates to the rest of the Universe. We suggest that the temperature increase in the shock provides the ingredients for hotspot electroweak baryogenesis. This also explains why baryons and DM have comparable densities, the precise ratio depending on the size of the PBH relative to the cosmological horizon at formation. The observed value of the collapse fraction and baryon asymmetry depends on the amplitude of the curvature fluctuations that generate the PBHs and may be explained by an anthropic selection effect associated with the existence of galaxies. We propose a scenario in which the quantum fluctuations of a light stochastic spectator field during inflation generate large curvature fluctuations in some regions, with the stochasticity of this field providing the basis for the required selection. Finally, we identify several observational predictions of our scenario that should be testable within the next few years. In particular, the PBH mass function could extend to sufficiently high masses to explain the black hole coalescences observed by LIGO/Virgo.

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Dark Stars: Dark matter in the first stars leads to a new phase of stellar evolution

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308024575 ◽

2008 ◽

Vol 4 (S255) ◽

pp. 56-60 ◽

Cited By ~ 1

Author(s):

Katherine Freese ◽

Douglas Spolyar ◽

Anthony Aguirre ◽

Peter Bodenheimer ◽

Paolo Gondolo ◽

...

Keyword(s):

Black Holes ◽

Dark Matter ◽

Cross Section ◽

Stellar Evolution ◽

Weakly Interacting Massive Particles ◽

First Stars ◽

History Of ◽

Born Again ◽

The Universe ◽

New Phase

AbstractThe first phase of stellar evolution in the history of the universe may be Dark Stars, powered by dark matter heating rather than by fusion. Weakly interacting massive particles, which are their own antiparticles, can annihilate and provide an important heat source for the first stars in the the universe. This talk presents the story of these Dark Stars. We make predictions that the first stars are very massive (~800M⊙), cool (6000 K), bright (~106L⊙), long-lived (~106years), and probable precursors to (otherwise unexplained) supermassive black holes. Later, once the initial DM fuel runs out and fusion sets in, DM annihilation can predominate again if the scattering cross section is strong enough, so that a Dark Star is born again.

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