Extracting Information about the Initial State from the Black Hole Radiation

Lochan, Kinjalk; Padmanabhan, Τ.

doi:10.1103/physrevlett.116.051301

Cited by 18 publications

(22 citation statements)

References 29 publications

(33 reference statements)

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“…Further a similar kind of identity can be obtained from the symmetry 12 generalized for complex F (y) 6 . Again, it is easily seen that any algebraic observable of y will be completely determined if the initial state belongs to this class.…”

Section: Multiply Excited Statesmentioning

confidence: 99%

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Non-vacuum states in QFT: Implications for Hawking radiation

Lochan¹,

Padmanabhan²

2017

The Fourteenth Marcel Grossmann Meeting

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We discuss the imprints of the initial quantum state, describing a matter chunk thrown into a black hole, contained in the the black hole radiation. We show that such a matter, described through non vacuum states in QFT, leads to distortions of the Hawking radiation from being exactly thermal. Using these distortions, we can uncover a specific amount of information about the initial state apart from its classical charges. For a large class of initial states, some specific observables defined in the initial Hilbert space are completely determined from the resulting final spectrum. We identify the class of instates which can be fully reconstructed from the information contained in the distortions at the semiclassical level. The Information lossHawking 1 , showed that quantum effects in the semiclassical regime could give rise to pairs of positive and negative energy particles, from the vacuum. While the negative energy particle falls into the event horizon and decreases the black hole mass, the positive energy particle travels to the asymptotic region and appears as Hawking radiation. This leads to the interpretation that the mass lost by the black hole in the process, reappears in the form of the energy of this radiation. In this process, since the pair popped out of vacuum state together, the out-going modes remain entangled with the in-going modes entering the horizon. But if the black hole evaporates completely by this process, there is nothing left for the outgoing modes to remain entangled with! Yet, they are in a mixed (thermal) state. This process, in which a pure state evolves into a mixed state, is contrary to the unitary quantum evolution 3 . It must be noted that though there exist multiple sources of distortions to the thermal Hawking radiation 4 , capable of making the pair non-maximally entangled, none of these will be strong enough to make the theory unitary 2 . So the crux of the information paradox can be summarized as follows. When the black hole evaporates completely without leaving any remnant, one is justified in assuming that the entire information content of the collapsing body must be encoded in the resulting radiation. However, remnant radiation in this process is dominantly thermal, which is thermodynamically prohibited to contain much of information. Therefore, the information content of the matter which made the black hole in the first place, along with whatever fell into it, seems inexplicably lost.We argue that this version of paradox possibly stems from an incomplete quantum analysis of a process which is truly fully quantum mechanical in nature. When an event horizon is formed the quantum field residing in its vacuum at the beginning of collapse, gradually erases the black hole through a negative energy flux into the horizon. However, the classical matter which forms a black hole is also funda-

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Section: Multiply Excited Statesmentioning

confidence: 99%

“…One can show 6,8 that most of the information content of the initial state will be lying in the IR sector of the radiation as the distortions die down towards the UV end of the spectrum.…”

Section: Radiation From Collapsementioning

confidence: 99%

Non-vacuum states in QFT: Implications for Hawking radiation

Lochan¹,

Padmanabhan²

2017

The Fourteenth Marcel Grossmann Meeting

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“…In fact this expectation fails at quantum scrutiny, not only due to existence of soft hairs we just discussed above, but otherwise as well. Even the semiclassical analysis of the matter field outside the horizon, shows its dependence on the part which resides inside the black hole [198,199], thus carrying the imprint outside and also questioning the factorizability of the Hilbert space as usually done : outside ⊗ inside.…”

Section: Hard (Quantum) Hairs On Black Holes?mentioning

confidence: 99%

Black Holes: Eliminating Information or Illuminating New Physics?

Chakraborty

Lochan

2017

Universe

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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...

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“…The analysis of the spectrum operator [19,31] also captures this distortion. The extraction of information about initial data using the spectral distortion N Ω = Ψ|b † Ωb Ω |Ψ − 0|b † Ωb Ω |0 , as reported in [24] is presented in detail in Appendix A. In Appendix B and Appendix C, we show that for a particular class of symmetric initial states, interesting quantities can be obtained from the out-states as well as their generalization for multi-particle states.…”

Section: Radiation From Black Hole: Information About the Initialmentioning

confidence: 99%

Information Retrieval from Black Holes

Chakraborty¹

2017

Springer Theses

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It is generally believed that, when matter collapses to form a black hole, the complete information about the initial state of the matter cannot be retrieved by future asymptotic observers, through local measurements. This is contrary to the expectation from a unitary evolution in quantum theory and leads to (a version of) the black hole information paradox. Classically, nothing else, apart from mass, charge and angular momentum is expected to be revealed to such asymptotic observers after the formation of a black hole. Semi-classically, black holes evaporate after their formation through the Hawking radiation. The dominant part of the radiation is expected to be thermal and hence one cannot know anything about the initial data from the resultant radiation. However, there can be sources of distortions which make the radiation non-thermal. Although the distortions are not strong enough to make the evolution unitary, these distortions carry some part of information regarding the in-state. In this work, we show how one can decipher the information about the in-state of the field from these distortions. We show that the distortions of a particular kind -which we call non-vacuum distortions -can be used to fully reconstruct the initial data. The asymptotic observer can do this operationally by measuring certain well-defined observables of the quantum field at late times. We demonstrate that a general class of in-states encode all their information content in the correlation of late time out-going modes. Further, using a 1 + 1 dimensional CGHS model to accommodate back-reaction self-consistently, we show that observers can also infer and track the information content about the initial data, during the course of evaporation, unambiguously. Implications of such information extraction are discussed.

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Extracting Information about the Initial State from the Black Hole Radiation

Cited by 18 publications

References 29 publications

Non-vacuum states in QFT: Implications for Hawking radiation

Non-vacuum states in QFT: Implications for Hawking radiation

Black Holes: Eliminating Information or Illuminating New Physics?

Information Retrieval from Black Holes

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