Quantum Hair from Gravity
Xavier Calmet, Roberto Casadio, Stephen D. H. Hsu, and Folkert Kuipers
Phys. Rev. Lett. 128, 111301 – Published 17 March 2022
We explore the relationship between the quantum state of a compact matter source and of its asymptotic graviton field. For a matter source in an energy eigenstate, the graviton state is determined at leading order by the energy eigenvalue. Insofar as there are no accidental energy degeneracies there is a one to one map between graviton states on the boundary of spacetime and the matter source states. Effective field theory allows us to compute a purely quantum gravitational effect which causes the subleading asymptotic behavior of the graviton state to depend on the internal structure of the source. This establishes the existence of ubiquitous quantum hair due to gravitational effects.The paper establishes that the quantum state of the graviton field (equivalently, the spacetime metric) of a compact matter source depends on the quantum state of the source. This can be established without a short distance theory of quantum gravity -- i.e., near the Planck length. Our results are long wavelength effects and are insensitive to the details of short distance physics, such as whether gravitons are excitations of strings, or something else, at the most fundamental level.
Quantum hair and black hole information
Physics Letters B Volume 827, 10 April 2022, 136995
Xavier Calmet and Stephen D.H. Hsu
It has been shown that the quantum state of the graviton field outside a black hole horizon carries information about the internal state of the hole. We explain how this allows unitary evaporation: the final radiation state is a complex superposition which depends linearly on the initial black hole state. Under time reversal, the radiation state evolves back to the original black hole quantum state. Formulations of the information paradox on a fixed semiclassical geometry describe only a small subset of the evaporation Hilbert space, and do not exclude overall unitarity.
Note to experts: the companion paper explains why Mathur's Theorem (i.e., entanglement entropy must always increase by ~ln 2 with each emitted qubit) is evaded once one considers BH evolution in the full radiation Hilbert space. The radiation Hilbert space is much larger than the small subspace which remains after conditioning on any specific spacetime background or BH recoil trajectory. Even exponentially small entanglement between different radiation states (mediated by quantum hair) can unitarize the evaporation process.
This is also explained in detail in the talk video and slides linked below.
Press coverage:
Earlier discussion, with more background on the Hawking paradox. See especially the important work by Suvrat Raju and collaborators:
Quantum Hair and Black Hole Information (December 2021)
Full transcript at Richard's substack.Begin: American society, growing up as child of immigrants18m: Russia-Ukraine conflict (eve of invasion), geopolitical implications (China, India, Germany, EU)38m: Affirmative Action, Harvard case at SCOTUS54m: Woke leftists at the university, destruction of meritocracy, STEM vs Social Justice advocacy, Sokal Hoax1h25m: Academic economics, 2008 credit crisis, Do economists test theories?1h33m: Maverick thinking, Agreeableness, Aspergers, Pressure to conform1h39m: Far-tail intelligence, Jeff Bezos and physics, progress in science and technology
Genomic Prediction’s Stephen Hsu: Making superhumans will be possible
The Sunday Times’ tech correspondent Danny Fortson brings on Stephen Hsu, co-founder of Genomic Prediction, to talk about the plummeting price of genomic sequencing (5:00), predicting height and cancer (9:10), mining biobanks (14:25), scoring embryos (19:00), why investors are staying anonymous (28:00), the need for a society-wide discussion (32:30), when he was accused of being a eugenicist (37:25), how powerful genetic prediction can be (43:15), genetic engineering (49:45), and why Denmark is the future (59:30).
Physicist, startup founder, and polymath Steve Hsu discusses the end of the unipolar moment, the return of geopolitics, and the U.S.-China New Cold War. He believes China is not as fragile as some say. We talk Taiwan, how Beijing has caught up in military tech, and how the nature of naval warfare in the next war will be very different. On the technology and AI front, he feels the U.S. and China are at parity, but that the long-term trend is in China's favor. He feels the social credit system is advancing just as fast in the West as in China and that the digital yuan is rapidly gaining in stature. He gives his view on the Ukraine crisis and how it has been a huge strategic error by the U.S. because it has cemented the Eurasian alliance. He's concerned about a systemic financial meltdown, discusses being a victim of woke cancel culture, and knowing Richard Feynman.
Two years ago, Burns wrote a memoir entitled, The Back Channel. It directly contradicts the argument being proffered by the administration he now serves. In his book, Burns says over and over that Russians of all ideological stripes—not just Putin—loathed and feared NATO expansion. He quotes a memo he wrote while serving as counselor for political affairs at the US embassy in Moscow in 1995. ‘Hostility to early NATO expansion,” it declares, “is almost universally felt across the domestic political spectrum here.” On the question of extending NATO membership to Ukraine, Burns’ warnings about the breadth of Russian opposition are even more emphatic. “Ukrainian entry into NATO is the brightest of all redlines for the Russian elite (not just Putin),” he wrote in a 2008 memo to then-Secretary of State Condoleezza Rice. “In more than two and a half years of conversations with key Russian players, from knuckle-draggers in the dark recesses of the Kremlin to Putin’s sharpest liberal critics, I have yet to find anyone who views Ukraine in NATO as anything other than a direct challenge to Russian interests.”
While the Biden administration claims that Putin bears all the blame for the current Ukraine crisis, Burns makes clear that the US helped lay its foundations. By taking advantage of Russian weakness, he argues, Washington fueled the nationalist resentment that Putin exploits today. Burns calls the Clinton administration’s decision to expand NATO to include Poland, Hungary, and the Czech Republic “premature at best, and needlessly provocative at worst.” And he describes the appetite for revenge it fostered among many in Moscow during Boris Yeltsin’s final years as Russia’s president. “As Russians stewed in their grievance and sense of disadvantage,” Burns writes, “a gathering storm of ‘stab in the back’ theories slowly swirled, leaving a mark on Russia’s relations with the West that would linger for decades.”
As the Bush administration moved toward opening NATO’s doors to Ukraine, Burns’ warnings about a Russian backlash grew even starker. He told Rice it was “hard to overstate the strategic consequences” of offering NATO membership to Ukraine and predicted that “it will create fertile soil for Russian meddling in Crimea and eastern Ukraine.” Although Burns couldn’t have predicted the specific kind of meddling Putin would employ—either in 2014 when he seized Crimea and fomented a rebellion in Ukraine’s east or today—he warned that the US was helping set in motion the kind of crisis that America faces today. Promise Ukraine membership in NATO, he wrote, and “There could be no doubt that Putin would fight back hard.”
Were a reporter to read Burns’ quotes to White House press secretary Jen Psaki today, she’d likely accuse them of “parroting Russian talking points.” But Burns is hardly alone. From inside the US government, many officials warned that US policy toward Russia might bring disaster. William Perry, Bill Clinton’s Defense Secretary from 1994 to 1997, almost resigned because of his opposition to NATO expansion. He has since declared that because of its policies in the 1990s, “the United States deserves much of the blame” for the deterioration in relations with Moscow. Steven Pifer, who from 1998 to 2000 served as US ambassador to Ukraine, has called Bush’s 2008 decision to declare that Ukraine would eventually join NATO “a real mistake.” Fiona Hill, who gained fame during the Trump impeachment saga, says that as national intelligence officers for Russia and Eurasia she and her colleagues “warned” Bush that “Putin would view steps to bring Ukraine and Georgia closer to NATO as a provocative move that would likely provoke pre-emptive Russian military action.”Oh, there's some historical background to all this? Some context? Wait I'm told every day this crisis just happened because Putin went crazy and wants to rebuild the USSR / Russian Empire.
Quantum hair and black hole information
https://doi.org/10.1016/j.physletb.2022.136995
Abstract
It has been shown that the quantum state of the graviton field outside a black hole horizon carries information about the internal state of the hole. We explain how this allows unitary evaporation: the final radiation state is a complex superposition which depends linearly on the initial black hole state. Under time reversal, the radiation state evolves back to the original black hole quantum state. Formulations of the information paradox on a fixed semiclassical geometry describe only a small subset of the evaporation Hilbert space, and do not exclude overall unitarity.The earlier paper, which established the existence of quantum hair, has been accepted by PRL and should also appear soon.
4. Conclusion
Hawking's information paradox has been the focus of intense interest for almost 50 years. In his 1992 lecture on the subject, John Preskill wrote [5]
I conclude that the information loss paradox may well presage a revolution in fundamental physics.
The resolution described here is conservative: the quantum state of the exterior gravity field is determined by the interior black hole state, allowing the latter to influence Hawking radiation produced at the horizon. Two distinct quantum states of the black hole may produce the same semiclassical external geometry, but the graviton states differ at the quantum level. The relationship between interior and exterior quantum states is not governed by classical no-hair theorems. Indeed, it has gradually been appreciated that gravity itself prevents the localization of quantum information [4], [9], [10], [11], [21], [22], [23], even behind a horizon. We stress that all formulations of the paradox require a degree of factorization between the black hole internal state and the radiation (see, e.g., (6)), which is clearly not true of our equation (4).
Certain aspects of our expressions (2)-(4) are very clear: the black hole information is spread over many branches of the final radiation state, and macroscopic superpositions of different spacetime geometries play a role in the evaporation. Some of the difficulty in resolving the paradox may originate from a reluctance to accept these aspects of quantum dynamics.
