Tag Archives: black holes

Movie Review of Interstellar, by Richard Price

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Image copyright Warner Bros and Paramount Pictures

CQG has never published a movie review before. It is therefore with appropriate humility that I offer a review of Interstellar.  This scifi epic wins the historic honor because it lists a physicist, Kip Thorne, as an executive producer, and is advertised as based on his theories. Indeed, the movie plot and graphics do involve ideas of relativity in very important ways.

In the spirit of disclosure I state, right up front, that I am not a fan of science fiction, but am a fan of Kip Thorne; like many of his former students I have remained a friend.  My fan/antifan biases should cancel and leave me to do the objective job that a scientist is expected to do.

This is not, of course, a review for the general public. CQG is seldom found in the waiting room of dentists. If you Continue reading →

Black holes as beads on cosmic strings

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Amjad Ashoorioon and Robert Mann

Amjad Ashoorioon (left) is a Senior Research Associate at the physics department of Lancaster University in the United Kingdom. Robert B. Mann (right) is a Professor of Physics and Applied Mathematics at the University of Waterloo, Ontario, Canada.

Cosmic strings have been a source of fascination in cosmology since Tom Kibble first proposed their existence 40 years ago. Like an imperfection in a solidifying crystal, a cosmic string is a thread of energy that might have formed in the early universe during a symmetry breaking phase transition. Twenty years ago Ruth Gregory pointed out that a black hole could have a cosmic string as a single “hair”.   Turning this idea around, in this article we have proposed that a Continue reading →

The Weyl curvature and the Cosmic Censorship conjecture

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Parampreet Singh

Parampreet Singh is an Assistant Professor of Physics at Louisiana State University

Whether the gravitational collapse of an astrophysical object leads to a black hole or a naked singularity is one of the most intriguing issues in Einstein’s theory of General Relativity. In many astrophysical situations, the initial conditions are such that a trapped region forms and the gravitational collapse ends in a black hole, in confirmation with the Cosmic Censorship conjecture. However, in recent years Continue reading →

Black hole voyeurism

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Alexander Smith and Robert Mann

Alexander (right) is a PhD student in the department of Physics & Astronomy at the University of Waterloo. Robert (left), a past-president of the Canadian Association of Physicists, is a senior professor in the department of Physics & Astronomy and the department of Applied Mathematics at the University of Waterloo and an affiliate at the Perimeter Institute.

Could a quantum detector peek inside a black hole?

It has long been known that the thermal radiation emitted by a black hole can be detected by a particle detector, and even today the details of this process are an active area of research. But are such detectors sensitive to the interior structure of black holes? From a classical perspective, conventional wisdom would suggest not: the topological censorship theorem relegates all isolated topological structures (such as wormholes, topological knots, etc) to be hidden behind a horizon and thus inaccessible to observers by classical probes. But Continue reading →

Homogeneous cosmological model from a discrete matter distribution

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Mikolaj Korzynski

Mikolaj Korzynski is an Assistant Professor at the Center of Theoretical Physics
of the Polish Academy of Sciences, Warsaw

How does a homogeneous FLRW metric arise from a cosmological model with black holes as the only source of gravitational field?

In astrophysical applications of general relativity we often need to apply the Einstein’s field equations to situations where the matter distribution, and consequently also the metric tensor, has a complicated form with relatively smooth large scale behavior and a  complicated structure on smaller scales. The problems of this kind are usually approached in the following way: instead of solving the equations directly we apply them to an idealized metric with the small-scale structure removed by Continue reading →

Black holes dual to exotic superconductors

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Figure 2c

Each point under the blue curve corresponds to a superconducting p-wave black hole with a helical structure at temperature T and with helical pitch 2πk. The red line denotes the thermodynamically preferred black holes which have the smallest free energy at a given temperature. The black holes exhibit a reversal of the direction of the helical pitch at T~ 0.04.

The gauge-gravity correspondence provides a fascinating theoretical framework for investigating non-perturbative features of strongly coupled quantum systems using weakly coupled dual gravitational descriptions in one lower space-time dimension. In particular, the thermodynamic phase structure of the quantum system is obtained by finding the black hole solutions with the smallest free energy. Such studies have led to the discovery of fundamentally new classes of black hole solutions and it is hoped that these endeavours will lead to new insights into exotic materials which are observed in nature. Continue reading →

Boundary states in higher-dimensional loop quantum gravity

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Higher-dimensional Chern-Simons theory appears in the description of isolated horizon boundaries in higher-dimensional General Relativity.

It is a well-known fact that the presence of boundaries (“edges”) leads to the concept of boundary states, which e.g. ensure gauge invariance for parallel transporters ending on the boundary. Most famously, the quantum Hall effect can be explained using such states. In the context of black hole (quantum) physics, boundary states are important since they are microscopic states associated to the horizon of the black hole. Counting such boundary states in agreement with the macroscopic properties of a black hole is thus a good candidate for a microscopic explanation of the Bekenstein-Hawking entropy. This paradigm has been successfully employed in 3+1 dimension in the context of loop quantum gravity, a canonical quantisation of General Relativity. Continue reading →