Georgi Dvali

Theoretical Particle Physics

Ludwig-Maximilians-Universität München

Faculty of Physics | Theoretical Particle Physics

Theresienstraße 37

80333 München

+49 89 2180 4549


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Members: Gia Dvali, Lukas Eisemann, Georgios Karananas, Marco Michel, Florian Kühnel, Sebastian Zell*

We are theoretical particle physicists working in Physics Beyond the Standard Model. Thus, our main goal is to understand the fundamental laws of Nature and to link them with experimental signatures in high energy particle accelerators, cosmology and astrophysics. Additionally, we have a very strong interest in many-body quantum systems and quantum information. We have established a link between these two subject areas through black holes and cosmology.

Black holes and cosmology

First, black holes are unique connectors of gravity and quantum information. The reason is that due to their Bekenstein-Hawking entropy, black holes possess a maximal capacity of information storage. Moreover, there exists increasing evidence that macroscopic black holes play the key role in the unitarization of collision processes of elementary particles at energies much higher than the Planck mass – a phenomenon that is sometimes called classicalization. It is therefore absolutely crucial for particle physics to understand how black holes work at the microscopic level.

Of course, the dream program would be to manufacture black holes in accelerator experiments with particle collisions. This prospect, however, is rather dim unless Nature was generous by lowering the scale where quantum gravity effects become strong down to Tera-eV energies [1]. Only in this situation, LHC is able to create black holes, as predicted in [2]. Whether this was the case, we will only learn after the LHC data analysis will be completed and/or after a next generation of accelerators with higher collision energy starts operating.

In this light, alternative routes for understanding microscopic black hole physics become especially important. Our key idea is that the mechanism responsible for the large black hole entropy could be much more general and also occur in many-body quantum systems that are not connected to gravity, such as certain Bose-Einstein condensates. Thus, those systems can provide an alternative laboratory for shedding new light on basic principles of information storage and processing by black holes. This approach allows both to simulate black hole quantum information features as well as to generalize them to other contexts. The great advantage of many-body quantum systems is that they are much easier to control both in experiment and in theory.

Moreover, those systems can also be connected to cosmology. According to the commonly accepted inflationary paradigm, the early Universe went through a quasi-de Sitter state. De Sitter spacetime exhibits some close similarities to a black hole. For example, similarly to the black hole entropy, a de Sitter Hubble patch carries a microstate entropy called Gibbons-Hawking entropy. Our idea is that due to this entropy, de Sitter represents a critical state of enhanced memory capacity and therefore is subject to analogous phenomena as black holes and other systems within this universality class. This view has important implications for early cosmology as it opens up some qualitatively new ways of accessing our Universe’s very distant past, which is not possible within the standard semi-classical treatment of inflation. In particular, we have argued [8] that our Universe must have carried a primordial quantum memory pattern encoded in the microstate of those degrees of freedom that are responsible for the Gibbons-Hawking entropy. This pattern – due to a so-called memory burden effect – must have been imprinted in higher order correlators of density perturbations, thereby providing future observations with an exceptional opportunity of decoding this primordial quantum information.

The key idea of our framework [3] that makes the connection of high energy physics and many-body quantum systems very concrete is that macroscopic black holes and de Sitter spaces actually possess a fundamental description as many-body systems. Namely, they represent states of soft gravitons with very high occupation number. Both gravitational systems are at a very special quantum critical point where the quantum interaction strength of soft gravitons (which is minuscule) is almost exactly compensated by their enormously-high occupation number [4]. In this way, the key to understanding the mysterious quantum properties of black holes and de Sitter lies in their multi-particle nature at criticality. Thus, our picture naturally links black holes or the Universe itself with other systems with high occupation number of bosons such as Bose-Einstein condensates or coherent states at criticality. We therefore can gain a valuable interdisciplinary knowledge by studying the behavior of such systems.

Exemplary lines of our research include

Decoherence time as a function of the coupling in a concrete prototype system. The critical point of enhanced memory storage is marked by a significant increase of the decoherence time of the stored information. Decoherence time as a function of the coupling in a concrete prototype system. The critical point of enhanced memory storage is marked by a significant increase of the decoherence time of the stored information. © Dvali group
1. General methods and prototype systems (see [5])
One of our key objectives is to develop methods for the theoretical study of information storage in many-body quantum systems. In particular, we aim to find and analyze critical states of enhanced information storage capacity. Both analytical and numerical methods play a key role. We use those to study prototype models with the ultimate goal of constructing systems that can be observed experimentally.

Graphic representing Hawking radiation of a black hole as many-body quantum phenomenon. Two of the N constituents of a black hole scatter and thereby produce a Hawking quantum. Hawking radiation of a black hole as many-body quantum phenomenon. Two of the N constituents of a black hole scatter and thereby produce a Hawking quantum. © Dvali group
2. Quantum breaking (see [6])

Although any fundamental description of a physical systems needs to include quantum mechanics, the classical approximation works well in many contexts. However, it is of crucial importance to understand when a classical formulation breaks down, i.e., when the true quantum evolution deviates from the classical description. This amounts to quantum breaking. Many-body (quantum) systems are the ideal testground for the theoretical and experimental study of this phenomenon, because a fundamental quantum description is available for them. Quantum breaking has particularly important implications for black hole physics. That their classical description is expected to break down after half evaporation is key to understanding how black holes process information. The phenomenon of quantum breaking in a sense has even more dramatic consequences for de Sitter and inflationary cosmologies as it shows that contrary to the standard semi-classical view such Universes cannot be eternal and literally are subjected to the process of aging due to quantum effects [7].

Graphich illustrationg a quantum substructure of de Sitter. Also this spacetime must possess a microscopic explanation for its entropy. A quantum substructure of de Sitter. Also this spacetime must possess a microscopic explanation for its entropy. © Dvali group
3. De Sitter and inflation (see [8])

As explained, de Sitter space exhibits great analogies to black holes, in particular because of its Gibbons-Hawking entropy. Therefore, our studies of information storage in analogue many-body quantum systems can equally be used to draw conclusions about this spacetime. For inflationary cosmology, this has important consequences both for fundamental understanding of Universe’s cosmological history as well as for observations. In particular, we predict the existence of primordial quantum memories that are carried through the entire inflationary history and are potentially observable.


[1] N. Arkani-Hamed, S. Dimopoulos and G. R. Dvali, “The Hierarchy problem and new dimensions at a millimeter”, Phys. Lett. B 429 (1998) 263, arXiv:hep-ph/9803315.
[2] I. Antoniadis, N. Arkani-Hamed, S. Dimopoulos and G. R. Dvali, “New dimensions at a millimeter to a Fermi and superstrings at a TeV,” Phys. Lett. B 436 (1998) 257, arXiv:hep-ph/9804398.
[3] G. Dvali, C. Gomez, “Black Hole’s Quantum N-Portrait”, Fortsch. Phys. 61 (2013) 742, arXiv:1112.3359 [hep-th].
[4] G. Dvali, C. Gomez, “Black Holes as Critical Point of Quantum Phase Transition”, Eur. Phys. J. C 74 (2014) 2752, arXiv:1207.4059 [hep-th].
[5] G. Dvali, M. Michel, S. Zell, “Finding Critical States of Enhanced Memory Capacity in Attractive Cold Bosons”, Eur. Phys. J. Quantum Technology 6 (2019) 1, arXiv:1805.10292 [quant-ph].
[6] G. Dvali, D. Flassig, C. Gomez, A. Pritzel, N. Wintergerst, “Scrambling in the Black Hole Portrait”, Phys. Rev. D 88 (2013) 124041, arXiv:1307.3458 [hep-th].
[7] G. Dvali, C. Gomez, “Quantum Compositeness of Gravity: Black Holes, AdS and Inflation”, JCAP 1401 (2014) 023, arXiv:1312.4795 [hep-th].
G. Dvali, C. Gomez and S. Zell, “Quantum Break-Time of de Sitter,” JCAP 1706 (2017) 028, arXiv:1701.08776 [hep-th].
[8] G. Dvali, L. Eisemann, M. Michel, S. Zell, “Universe’s Primordial Quantum Memories”, JCAP 1903 (2019) 010, arXiv:1812.08749 [hep-th].

*external collaborator | École polytechnique fédérale de Lausanne


Primordial black holes from confinement

G. Dvali, F. Kühnel, M. Zantedeschi

Physical Review D 104, 123507 (2021).

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A mechanism for the formation of primordial black holes is proposed. Here, heavy quarks of a confining gauge theory produced by de Sitter fluctuations are pushed apart by inflation and get confined after horizon reentry. The large amount of energy stored in the color flux tubes connecting the quark pair leads to black-hole formation. These are much lighter and can be of higher spin than those produced by standard collapse of horizon-size inflationary overdensities. Other difficulties exhibited by such mechanisms are also avoided. Phenomenological features of the new mechanism are discussed as well as accounting for both the entirety of the dark matter and the supermassive black holes in the galactic centers. Under proper conditions, the mechanism can be realized in a generic confinement theory, including ordinary QCD. We discuss a possible string-theoretic realization via D-branes. Interestingly, for conservative values of the string scale, the produced gravity waves are within the range of recent NANOGrav data. Simple generalizations of the mechanism allow for the existence of a significant scalar component of gravity waves with distinct observational signatures.

DOI: 10.1103/PhysRevD.104.123507

Entropy bound and unitarity of scattering amplitudes

G. Dvali

JHEP 3, 126 (2021).

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We establish that unitarity of scattering amplitudes imposes universal entropy bounds. The maximal entropy of a self-sustained quantum field object of radius R is equal to its surface area and at the same time to the inverse running coupling α evaluated at the scale R. The saturation of these entropy bounds is in one-to-one correspondence with the non-perturbative saturation of unitarity by 2 → N particle scattering amplitudes at the point of optimal truncation. These bounds are more stringent than Bekenstein’s bound and in a consistent theory all three get saturated simultaneously. This is true for all known entropy-saturating objects such as solitons, instantons, baryons, oscillons, black holes or simply lumps of classical fields. We refer to these collectively as saturons and show that in renormalizable theories they behave in all other respects like black holes. Finally, it is argued that the confinement in SU(N) gauge theory can be understood as a direct consequence of the entropy bounds and unitarity.

DOI: 10.1007/JHEP03(2021)126

S-Matrix and Anomaly of de Sitter

G. Dvali

Symmetry 13, 3 (2020).

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S-matrix formulation of gravity excludes de Sitter vacua. In particular, this is organic to string theory. The S-matrix constraint is enforced by an anomalous quantum break-time proportional to the inverse values of gravitational and/or string couplings. Due to this, de Sitter can satisfy the conditions for a valid vacuum only at the expense of trivializing the graviton and closed-string S-matrices. At non-zero gravitational and string couplings, de Sitter is deformed by corpuscular 1/N effects, similarly to Witten–Veneziano mechanism in QCD with N colors. In this picture, an S-matrix formulation of Einstein gravity, such as string theory, nullifies an outstanding cosmological puzzle. We discuss possible observational signatures which are especially interesting in theories with a large number of particle species. Species can enhance the primordial quantum imprints to potentially observable level even if the standard inflaton fluctuations are negligible.

DOI: 10.3390/sym13010003

Spontaneous conformal symmetry breaking in fishnet CFT

G. Karananas, V. Kazakov, M. Shaposhnikov

Phys. Lett. B 811, 135922 (2020).

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Quantum field theories with exact but spontaneously broken conformal invariance have an intriguing feature: their vacuum energy (cosmological constant) is equal to zero. Up to now, the only known ultraviolet complete theories where conformal symmetry can be spontaneously broken were associated with supersymmetry (SUSY), with the most prominent example being the =4 SUSY Yang-Mills. In this Letter we show that the recently proposed conformal “fishnet” theory supports at the classical level a rich set of flat directions (moduli) along which conformal symmetry is spontaneously broken. We demonstrate that, at least perturbatively, some of these vacua survive in the full quantum theory (in the planar limit, at the leading order of expansion) without any fine tuning. The vacuum energy is equal to zero along these flat directions, providing the first non-SUSY example of a four-dimensional quantum field theory with “natural” breaking of conformal symmetry.

DOI: 10.1016/j.physletb.2020.135922

Black hole metamorphosis and stabilization by memory burden

G. Dvali, L. Eisemann, M. Michel, S. Zell

Phys. Rev. D 102, 103523 (2020).

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Systems of enhanced memory capacity are subjected to a universal effect of memory burden, which suppresses their decay. In this paper, we study a prototype model to show that memory burden can be overcome by rewriting stored quantum information from one set of degrees of freedom to another one. However, due to a suppressed rate of rewriting, the evolution becomes extremely slow compared to the initial stage. Applied to black holes, this predicts a metamorphosis, including a drastic deviation from Hawking evaporation, at the latest after losing half of the mass. This raises a tantalizing question about the fate of a black hole. As two likely options, it can either become extremely long lived or decay via a new classical instability into gravitational lumps. The first option would open up a new window for small primordial black holes as viable dark matter candidates.

DOI: 10.1103/PhysRevD.102.103523

Unitarity Entropy Bound: Solitons and Instantons

G. Dvali

Fortsch. Phys. 69, 2000091 (2020).

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We show that non-perturbative entities such as solitons and instantons saturate bounds on entropy when the theory saturates unitarity. Simultaneously, the entropy becomes equal to the area of the soliton/instanton. This is strikingly similar to black hole entropy despite absence of gravity. We explain why this similarity is not an accident. We present a formulation that allows to apply the entropy bound to instantons. The new formulation also eliminates apparent violations of the Bekenstein entropy bound by some otherwise-consistent unitary systems. We observe that in QCD, an isolated instanton of fixed size and position violates the entropy bound for strong 't Hooft coupling. At critical 't Hooft coupling the instanton entropy is equal to its area.

DOI: 10.1002/prop.202000091

Compact Dark Matter Objects via N Dark Sectors

G. Dvali, E. Koutsangelas, F. Kühnel

Phys. Rev. D 101, 83533 (2020).

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We propose a novel class of compact dark matter objects in theories where the dark matter consists of multiple sectors. We call these objects N-MACHOs. In such theories neither the existence of dark matter species nor their extremely weak coupling to the observable sector represent additional hypotheses but instead are imposed by the solution to the Hierarchy Problem and unitarity. The crucial point is that particles from the same sector have non-trivial interactions but interact only gravitationally otherwise. As a consequence, the pressure that counteracts the gravitational collapse is reduced while the gravitational force remains the same. This results in collapsed structures much lighter and smaller as compared to the ordinary single-sector case. We apply this phenomenon to a dark matter theory that consists of N dilute copies of the Standard Model. The solutions do not rely on an exotic stabilization mechanism, but rather use the same well-understood properties as known stellar structures. This framework also gives rise to new microscopic superheavy structures, for example with mass 108g and size 10−13cm. By confronting the resulting objects with observational constraints, we find that, due to a huge suppression factor entering the mass spectrum, these objects evade the strongest constrained region of the parameter space. Finally, we discuss possible formation scenarios of N-MACHOs. We argue that, due to the efficient dissipation of energy on small scales, high-density regions such as ultra-compact mini-halos could serve as formation sites of N-MACHOs.

DOI: 10.1103/PhysRevD.101.083533

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