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Gia Dvali

Publications and source records attributed to Gia Dvali.

At least 91 records · Page 5Linked to original sources
arXiv2016

Aharonov-Bohm protection of black hole's baryon/skyrmion hair

The baryon/skyrmion correspondence implies that the baryon number is encoded into a topological surface integral. Under certain conditions that we clarify, this surface integral can be measured by an asymptotic observer in form of an Aharonov-Bohm phase-shift in an experiment in which the skyrmion passes through a loop of a probe string. In such a setup the baryon/skyrmion number must be respected by black holes, despite the fact that it produces no long-range classical field. If initially swallowed by a black hole, the baryon number must resurface in form of a classical skyrmion hair, after the black hole evaporates below a certain critical size. Needless to say, the respect of the baryon number by black holes is expected to have potentially-interesting astrophysical consequences.

hep-th↗
arXiv2016

Skyrmion Black Hole Hair: Conservation of Baryon Number by Black Holes and Observable Manifestations

We show that the existence of black holes with classical skyrmion hair invalidates standard proofs that global charges, such as the baryon number, cannot be conserved by a black hole. By carefully analyzing the standard arguments based on a Gedankenexperiment in which a black hole is seemingly-unable to return the baryon number that it swallowed, we identify inconsistencies in this reasoning, which does not take into the account neither the existence of skyrmion black holes nor the baryon/skyrmion correspondence. We then perform a refined Gedankenexperiment by incorporating the new knowledge and show that no contradiction with conservation of baryon number takes place at any stage of black hole evolution. Our analysis also indicates no conflict between semi-classical black holes and the existence of baryonic gauge interaction arbitrarily-weaker than gravity. Next, we study classical cross sections of a minimally-coupled massless probe scalar field scattered by a skyrmion black hole. We investigate how the skyrmion hair manifests itself by comparing this cross section with the analogous cross section caused by a Schwarzschild black hole which has the same ADM mass as the skyrmion black hole. Here we find an order-one difference in the positions of the characteristic peaks in the cross sections. The peaks are shifted to smaller scattering angles when the skyrmion hair is present. This comes from the fact that the skyrmion hair changes the near horizon geometry of the black hole when compared to a Schwarzschild black hole with same ADM mass. We keep the study of this second aspect general so that the qualitative results which we obtain can also be applied to black holes with classical hair of different kind.

hep-th↗
arXiv2016

Small neutrino masses from gravitational $θ$-term

We present how a neutrino condensate and small neutrino masses emerge from a topological formulation of gravitational anomaly. We first recapitulate how a gravitational $θ$-term leads to the emergence of a new bound neutrino state analogous to the $η'$ meson of QCD. Then we show the consequent formation of a neutrino vacuum condensate, which effectively generates small neutrino masses. Afterwards we outline several phenomenological consequences of our neutrino mass generation model. The cosmological neutrino mass bound vanishes since we predict the neutrinos to be massless until the phase transition in the late Universe, $T\sim {\rm meV}$. Deviations from an equal flavor rate due to enhanced neutrino decays in extraterrestrial neutrino fluxes can be observed in future IceCube data. The current cosmological neutrino background only consists of the lightest neutrinos, which, due to enhanced neutrino-neutrino interactions, either bind up, form a superfluid, or completely annihilate into massless bosons. Strongly coupled relic neutrinos could provide a contribution to cold dark matter in the late Universe, together with the new proposed particles and topological defects, which may have formed during neutrino condensation. These enhanced interactions could also be a source of relic neutrino clustering in our Galaxy, which possibly makes the overdense cosmic neutrino background detectable in the KATRIN experiment. The neutrino condensate provides a mass for the hypothetical $B-L$ gauge boson, leading to a gravity-competing force detectable in short-distance measurements. Gravitational waves detections have the potential to probe our neutrino mass generation mechanism.

hep-ph↗
arXiv2016

Strong Coupling and Classicalization

Classicalization is a phenomenon in which a theory prevents itself from entering into a strong-coupling regime, by redistributing the energy among many weakly-interacting soft quanta. In this way, the scattering process of some initial hard quanta splits into a large number of soft elementary processes. In short, the theory trades the strong coupling for a high-multiplicity of quanta. At very high energies, the outcome of such a scattering experiment is a production of soft states of high occupation number that are approximately classical. It is evident that black hole creation in particle collision at super-Planckian energies is a result of classicalization, but there is no a priory reason why this phenomenon must be limited to gravity. If the hierarchy problem is solved by classicalization, the LHC has a chance of detecting a tower of new resonances. The lowest-lying resonances must appear right at the strong coupling scale in form of short-lived elementary particles. The heavier members of the tower must behave more and more classically: they must be longer lived and decay into higher numbers of soft quanta.

hep-th↗
arXiv2016

Goldstone origin of black hole hair from supertranslations and criticality

Degrees of freedom that carry black hole entropy and hair can be described in the language of Goldstone phenomenon. They represent the pseudo-Goldstone bosons of certain supertranslations, called A-transformations, that are spontaneously broken by the black hole metric. This breaking gives rise to a tower of Goldstone bosons created by the spontaneously-broken generators that can be labeled by spherical harmonics. Classically, the number of charges is infinite, they have vanishing VEVs and the corresponding Goldstone modes are gapless. The resulting hair and entropy are infinite, but unresolvable. In quantum theory the two things happen. The number of legitimate Goldstone modes restricted by requirement of weak-coupling, becomes finite and scales as black hole area in Planck units. The Goldstones generate a tiny gap, controlled by their gravitational coupling. The gap turns out to be equal to the inverse of black hole half-life, $t_{BH}$. Correspondingly, in quantum theory the charges are neither conserved nor vanish, but non-conservation time is set by $t_{BH}$. This picture nicely matches with the idea of a black hole as of critical system composed of many soft gravitons. The A-Goldstones of geometric picture represent the near-gapless Bogoliubov-Goldstone modes of critical soft-graviton system.

hep-th↗
arXiv2016

Universality of Black Hole Quantum Computing

By analyzing the key properties of black holes from the point of view of quantum information, we derive a model-independent picture of black hole quantum computing. It has been noticed that this picture exhibits striking similarities with quantum critical condensates, allowing the use of a common language to describe quantum computing in both systems. We analyze such quantum computing by allowing coupling to external modes, under the condition that the external influence must be soft-enough in order not to offset the basic properties of the system. We derive model-independent bounds on some crucial time-scales, such as the times of gate operation, decoherence, maximal entanglement and total scrambling. We show that for black hole type quantum computers all these time-scales are of the order of the black hole half-life time. Furthermore, we construct explicitly a set of Hamiltonians that generates a universal set of quantum gates for the black hole type computer. We find that the gates work at maximal energy efficiency. Furthermore, we establish a fundamental bound on the complexity of quantum circuits encoded on these systems, and characterize the unitary operations that are implementable. It becomes apparent that the computational power is very limited due to the fact that the black hole life-time is of the same order of the gate operation time. As a consequence, it is impossible to retrieve its information, within the life-time of a black hole, by externally coupling to the black hole qubits. However, we show that, in principle, coupling to some of the internal degrees of freedom allows acquiring knowledge about the micro-state. Still, due to the trivial complexity of operations that can be performed, there is no time advantage over the collection of Hawking radiation and subsequent decoding.

hep-th↗
arXiv2016

Gravitational Black Hole Hair from Event Horizon Supertranslations

We discuss BMS supertranslations both at null-infinity and on the horizon for the case of the Schwarzschild black hole. We show that both kinds of supertranslations lead to infinetly many gapless physical excitations. On this basis we construct a quotient algebra using suited superpositions of both kinds of transformations which cannot be compensated by an ordinary BMS-supertranslation and therefore are intrinsically due to the presence of an event horizon. We show that these quotient transformations are physical and generate gapless excitations on the horizon that can account for the gravitational hair as well as for the black hole entropy. We identify the physics of these modes as associated with Bogolioubov-Goldstone modes due to quantum criticality. Classically the number of these gapless modes is infinite. However, we show that due to quantum criticality the actual amount of information-carriers becomes finite and consistent with Bekenstein entropy. Although we only consider the case of Schwarzschild geometry, the arguments are extendable to arbitrary space-times containing event horizons.

hep-th↗
arXiv2016

Black Hole Based Quantum Computing in Labs and in the Sky

Analyzing some well established facts, we give a model-independent parameterization of black hole quantum computing in terms of a set of macro and micro quantities and their relations. These include the relations between the extraordinarily-small energy gap of black hole qubits and important time-scales of information-processing, such as, scrambling time and Page's time. We then show, confirming and extending previous results, that other systems of nature with identical quantum informatics features are attractive Bose-Einstein systems at the critical point of quantum phase transition. Here we establish a complete isomorphy between the quantum computational properties of these two systems. In particular, we show that the quantum hair of a critical condensate is strikingly similar to the quantum hair of a black hole. Irrespectively whether one takes the similarity between the two systems as a remarkable coincidence or as a sign of a deeper underlying connection, the following is evident. Black holes are not unique in their way of quantum information processing and we can manufacture black hole based quantum computers in labs by taking advantage of quantum criticality.

hep-th↗
arXiv2015

Towards a Quantum Theory of Solitons

We formulate a quantum coherent state picture for topological and non-topological solitons. We recognize that the topological charge arises from the infinite occupation number of zero momentum quanta flowing in one direction. Thus, the Noether charge of microscopic constituents gives rise to a topological charge in the macroscopic description. This fact explains the conservation of topological charge from the basic properties of coherent states. It also shows that no such conservation exists for non-topological solitons, which have finite mean occupation number. Consequently, they can have an exponentially-small but non-zero overlap with the vacuum, leading to vacuum instability. This amplitude can be interpreted as a coherent state description of false vacuum decay. Next we show that we can represent topological solitons as a convolution of two sectors that carry information about topology and energy separately, which makes their difference very transparent. Finally, we show how interaction among the solitons can be understood from basic properties of quantum coherent states.

hep-th↗
arXiv2015

Stückelberg Formulation of Holography

We suggest that holography can be formulated in terms of the information capacity of the Stückelberg degrees of freedom that maintain gauge invariance of the theory in the presence of an information boundary. These Stückelbergs act as qubits that account for a certain fraction of quantum information. Their information capacity is measured by the ratio of the inverse Stückelberg energy gap to the size of the system. Systems with the smallest gap are maximally holographic. For massless gauge systems this information measure is universally equal to the inverse coupling evaluated at the systems' length scale. In this language it becomes very transparent why the Stückelberg information capacity of black holes saturates the Bekenstein bound and accounts for the entire information of the system. The physical reason is that the strength of quantum interaction is bounded from below by the gravitational coupling, which scales as area. Observing the striking similarity between the scalings of the energy gap of the boundary Stückelberg modes and the Bogoliubov modes of critical many-body systems, we establish a connection between holography and quantum criticality through the correspondence between these modes.

hep-th↗
arXiv2015

Classical Limit of Black Hole Quantum N-Portrait and BMS Symmetry

Black hole entropy, denoted by N, in (semi)classical limit is infinite. This scaling reveals a very important information about the qubit degrees of freedom that carry black hole entropy. Namely, the multiplicity of qubits scales as N, whereas their energy gap and their coupling as 1/N. Such a behavior is indeed exhibited by Bogoliubov-Goldstone degrees of freedom of a quantum-critical state of N soft gravitons (a condensate or a coherent state) describing the black hole quantum portrait. They can be viewed as the Goldstone modes of a broken symmetry acting on the graviton condensate. In this picture Minkowski space naturally emerges as a coherent state of infinite-N gravitons of infinite wavelength and it carries an infinite entropy. In this paper we ask what is the geometric meaning (if any) of the classical limit of this symmetry. We argue that the infinite-N limit of Bogoliubov-Goldstone modes of critical graviton condensate is described by recently-discussed classical BMS super-translations broken by the black hole geometry. However, the full black hole information can only be recovered for finite N, since the recovery time becomes infinite in classical limit in which N is infinite.

hep-th↗
arXiv2015

Black Hole Type Quantum Computing in Critical Bose-Einstein Systems

Recent ideas about understanding physics of black hole information-processing in terms of quantum criticality allow us to implement black hole mechanisms of quantum computing within critical Bose-Einstein systems. The generic feature, uncovered both by analytic and numeric studies, is the emergence at the critical point of gapless weakly-interacting modes, which act as qubits for information-storage at a very low energy cost. These modes can be effectively described in terms of either Bogoliubov or Goldstone degrees of freedom. The ground-state at the critical point is maximally entangled and far from being classical. We confirm this near-critical behavior by a new analytic method. We compute growth of entanglement and show its consistency with black hole type behavior. On the other hand, in the over-critical regime the system develops a Lyapunov exponent and scrambles quantum information very fast. By, manipulating the system parameters externally, we can put it in and out of various regimes and in this way control the sequence of information storage and processing. By using gapless Bogoliubov modes as control qubits we design some simple logic gates.

hep-th↗
arXiv2015

Nambu-Goldstone Effective Theory of Information at Quantum Criticality

We establish a fundamental connection between quantum criticality of a many-body system, such as Bose-Einstein condensates, and its capacity of information-storage and processing. For deriving the effective theory of modes in the vicinity of the quantum critical point we develop a new method by mapping a Bose-Einstein condensate of $N$-particles onto a sigma model with a continuous global (pseudo)symmetry that mixes bosons of different momenta. The Bogolyubov modes of the condensate are mapped onto the Goldstone modes of the sigma model, which become gapless at the critical point. These gapless Goldstone modes are the quantum carriers of information and entropy. Analyzing their effective theory, we observe the information-processing properties strikingly similar to the ones predicted by the black hole portrait. The energy cost per qubit of information-storage vanishes in the large-$N$ limit and the total information-storage capacity increases with $N$ either exponentially or as a power law. The longevity of information-storage also increases with $N$, whereas the scrambling time in the over-critical regime is controlled by the Lyapunov exponent and scales logarithmically with $N$. This connection reveals that the origin of black hole information storage lies in the quantum criticality of the graviton Bose-gas, and that much simpler systems that can be manufactured in table-top experiments can exhibit very similar information-processing dynamics.

hep-th↗
arXiv2014

Quantum Exclusion of Positive Cosmological Constant?

We show that a positive cosmological constant is incompatible with the quantum-corpuscular resolution of de Sitter metric in form of a coherent state. The reason is very general and is due to the quantum self-destruction of the coherent state because of the scattering of constituent graviton quanta. This process creates an irreversible quantum clock, which precludes eternal de Sitter. It also eliminates the possibility of Boltzmann brains and Poincare recurrences. This effect is expected to be part of any microscopic theory that takes into account the quantum corpuscular structure of the cosmological background. This observation puts the cosmological constant problem in a very different light, promoting it, from a naturalness problem, into a question of quantum consistency. We are learning that quantum gravity cannot tolerate exceedingly-classical sources.

hep-th↗
arXiv2014

Corpuscular Breaking of Supersymmetry

Are topological solitons elementary or composites? We answer this question by drawing up a corpuscular formalism in which solitons are coherent states of quantum constituents. This naturally leads to a functional integral representation, in which the classical saddle point is reached as the most probable distribution of corpuscles in the $\hbar = 0$ limit and where quantum corpuscular corrections correspond to excursions away from such a distribution that occur only for finite $\hbar$. Several striking features come up. Topological charge emerges as a collective flow of quantum numbers carried by individual corpuscles. Moreover, the corpuscular corrections are not reducible to any known form of quantum corrections, such as loop expansions in the coupling constant $\hbar g^2$ or semiclassical $e^{-1/\hbar g^2}$ effects. Corpuscular corrections are stronger and appear already at order $\sqrt{\hbar g^2}$. In SUSY theories quantum corpuscular corrections generically break supersymmetry. We show that a domain wall which perturbatively is a BPS state, violates all supersymmetries when the corpuscular effects are taken into account. The extension of the corpuscular structure to $D$-branes can lead to a built-in supersymmetry breaking mechanism in string theory, insensitive to technicalities such as moduli stabilization, with the SUSY breaking scale set by the string coupling times the $D$-brane tension.

hep-th↗
arXiv2014

BICEP2 in Corpuscular Description of Inflation

A corpuscular quantum description of inflation shows that there is no fundamental problem with trans-Planckian excursions of the inflaton field up to about 100 Planck masses, with the upper bound coming from the corpuscular quantum effects. In this description the r-parameter measures the ratio of occupation numbers of gravitons versus inflatons, which, according to BICEP2, was roughly a half at the time of 60 e-foldings prior to the end of inflation. We stress that in non-Wilsonian UV self-completion of gravity any trans-Planckian mode coupled to inflaton is a black hole. Unlike the Wilsonian case, their integration-out gives an exponentially-suppressed effect and is unable to prevent trans-Planckian excursions of the inflaton field.

astro-ph.CO↗
arXiv2013

On How Neutrino Protects the Axion

We show how the neutrino can sacrifice itself to quantum gravity and save the axion solution to the strong-CP problem. This mechanism puts an upper bound on the lightest neutrino mass.

hep-th↗