Black Holes: Eliminating Information or Illuminating New Physics?

Abstract

Black holes, initially thought of as very interesting mathematical and geometric solutions of general relativity, over time, have come up with surprises and challenges for modern physics. In modern times, they have started to test our confidence in the fundamental understanding of nature. The most serious charge on the black holes is that they eat up information, never to release and subsequently erase it. This goes absolutely against the sacred principles of all other branches of fundamental sciences. This realization has shaken the very base of foundational concepts, both in quantum theory and gravity, which we always took for granted. Attempts to get rid of of this charge, have led us to crossroads with concepts, hold dearly in quantum theory. The sphere of black hole's tussle with quantum theory has readily and steadily grown, from the advent of the Hawking radiation some four decades back, into domain of quantum information theory in modern times, most aptly, recently put in the form of the firewall puzzle. Do black holes really indicate something sinister about their existence or do they really point towards the troubles of ignoring the fundamental issues, our modern theories are seemingly plagued with? In this review, we focus on issues pertaining to black hole evaporation, the development of the information loss paradox, its recent formulation, the leading debates and promising directions in the community.Keywords: black hole physics; information loss paradox; quantum fields in curved background Being Simple is ComplexThe twentieth century was a time in theoretical physics when many innovative, visionary ideas gained firm ground. Experimental verifications of many remarkable ideas were, deservingly, celebrated as the decisive steps towards building a concrete understanding of nature. From the first decades of the century, two radically different but conceptually very profound ideas came out: Relativity-viewing space and time as a geometric fabric acting as stage on which everything else takes place-and Quantum theory-acknowledging the wave character of everything in the universe. These two theories came up with revolutionary and also beautiful insights which kept getting ratified time and again (without fail till date) by the most sophisticated experiments. However, they also did come with some radically counter-intuitive ideas at their cores. With the advent and the subsequent triumph of the quantum theory, we realized that determinism is not an intrinsic property of nature at the fundamental level and one needs to adopt the probabilistic interpretation for the most fundamental description. This feature of the new realization alone has caused certain unrest with the quantum theory, and has raised many discussion and proposals related to this particular character of the theory [1][2][3][4][5][6][7][8]. Relativity on the other hand, very beautifully describes gravity as an artifact of curvature of a fabric named the spacetime. Describing gravity as the curvature of the spacetime remarkably gives...

Bosons falling into a black hole: A superfluid analogue

“…We now look at the implications of this result for a black hole in its final stages of the evaporation process [1,3,4,15,25,26]. Our description of bosonic Andreev reflection from a normal fluid/superfluid BEC interface is quite similar to the ideas proposed by Horowtiz and Maldacena [1], and Preskill and Hayden [4] respectively, regarding how the quantum information encoded in the infalling matter can escape from a black hole past the "half-way" point in the evaporation process, where more that half of its initial entropy has been radiated away and a quantum final state description can be envisaged.…”

“…In laboratory settings, external parameters like temperature and pressure control give this stability to the condensate ground state, and we assume the boundary processes are also sufficiently low energy (ε → 0) not to perturb the condensate from its ground state. This observation should be read in the context of an earlier argument made by Prof. Susskind, as to how, in the gravity context, requiring validity of a local quantum field theory respecting linearity and unitarity of quantum physics makes the wavefunction of the interior of a black hole independent of the past and future Cauchy surfaces [25,26]. By satisfying certain symmetry requirements as discussed above, we find that the superfluid ground state of interacting bosons can qualify as this special quantum state to describe the final quantum state of bosons collapsing into a black hole past its "half-way" point in evaporation.…”

Andreev reflections and the quantum physics of black holes

“…A black hole reaches the "half way point" when it has already radiated half the initial entropy and cannot accept information anymore [2]. The information is reflected via Hawking radiation [3] very quickly, and it is speculated that quantum theories of gravity are necessary to understand the process [1,2,4,5]. Attempts to understand the quantum physics of black holes have led to interesting black hole analogies proposed and observed in a variety of experiments, including lasers [6,7], rapid change of dielectric constant in waveguides [8], and time-varying refractive index of a medium [9], moving plasma mirrors [10], sonic systems [11,12] and Bose-Einstein condensates [13].…”

Compact chiral boson fields on the horizon of BTZ black hole

“…Those incompressible quantum fluids and their excitations can be viewed as W 1+∞ edge conformal field theories, thus providing an algebraic classification of quantum Hall universality classes [14,15]. The W 1+∞ was used to classify the BTZ black holes and give the 'W-hairs' of black hole [16], which maybe essential to solve the information paradox [17][18][19]. But the origin of this W 1+∞ is unclear.…”