19 research outputs found
Falling Toward Charged Black Holes
The growth of the "size" of operators is an important diagnostic of quantum
chaos. In arXiv:1802.01198 [hep-th] it was conjectured that the holographic
dual of the size is proportional to the average radial component of the
momentum of the particle created by the operator. Thus the growth of operators
in the background of a black hole corresponds to the acceleration of the
particle as it falls toward the horizon. In this note we will use the
momentum-size correspondence as a tool to study scrambling in the field of a
near-extremal charged black hole. The agreement with previous work provides a
non-trivial test of the momentum-size relation, as well as an explanation of a
paradoxical feature of scrambling previously discovered by Leichenauer
[arXiv:1405.7365 [hep-th]]. Naively Leichenauer's result says that only the
non-extremal entropy participates in scrambling. The same feature is also
present in the SYK model. In this paper we find a quite different
interpretation of Leichenauer's result which does not have to do with any
decoupling of the extremal degrees of freedom. Instead it has to do with the
buildup of momentum as a particle accelerates through the long throat of the
Reissner-Nordstrom geometry.Comment: v4: typos correcte
Operator growth in the SYK model
We discuss the probability distribution for the "size" of a time-evolving
operator in the SYK model. Scrambling is related to the fact that as time
passes, the distribution shifts towards larger operators. Initially, the rate
is exponential and determined by the infinite-temperature chaos exponent. We
evaluate the size distribution numerically for , and show how to
compute it in the large- theory using the dressed fermion propagator. We
then evaluate the distribution explicitly at leading nontrivial order in the
large- expansion.Comment: 18 pages, 2 official figures, many unofficial figure
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Quantum Chaos, Operator Growth, and Holography
The exact role of the internal degrees of freedom (a.k.a. d.o.f.) in holography is not well-understood. Thus, in this thesis, we study a toy model of holography without space: the Sachdev-Ye-Kitaev (SYK) Model. This 0+1 theory of all possible 4-body interactions of N fermion "flavors"/"colors" features a low energy limit reproducing aspects of 1+1 Jackiw-Teitelboim gravity. First, we show that the inherent discreteness of the quantum spectrum results in universal late-time behavior due to eigenvalue repulsion. We then note that the theory's four-point functions probe the phenomenon of operator growth, where an internal d.o.f. goes on to epidemically evolve into larger products of internal d.o.f.s. In this manner where small operators smoothly grow into superpositions of increasing products of operators, we observe a sort of "size" locality, which is intimately tied with the notion of a conformal primary "descending" along its descendants. In fact, we find that the underlying structure of the SYK epidemic limits to that of a probe particle falling into a black hole. In other words, similar to how nearest neighbor interactions lead to dynamics on a flat space background, we demonstrate that many internal interactions lead to dynamics on a higher dimensional geometry
Black Holes and Random Matrices
We argue that the late time behavior of horizon fluctuations in large anti-de
Sitter (AdS) black holes is governed by the random matrix dynamics
characteristic of quantum chaotic systems. Our main tool is the
Sachdev-Ye-Kitaev (SYK) model, which we use as a simple model of a black hole.
We use an analytically continued partition function as well
as correlation functions as diagnostics. Using numerical techniques we
establish random matrix behavior at late times. We determine the early time
behavior exactly in a double scaling limit, giving us a plausible estimate for
the crossover time to random matrix behavior. We use these ideas to formulate a
conjecture about general large AdS black holes, like those dual to 4D
super-Yang-Mills theory, giving a provisional estimate of the crossover time.
We make some preliminary comments about challenges to understanding the late
time dynamics from a bulk point of view.Comment: 73 pages, 15 figures, minor errors correcte
Existential witness extraction in classical realizability and via a negative translation
We show how to extract existential witnesses from classical proofs using
Krivine's classical realizability---where classical proofs are interpreted as
lambda-terms with the call/cc control operator. We first recall the basic
framework of classical realizability (in classical second-order arithmetic) and
show how to extend it with primitive numerals for faster computations. Then we
show how to perform witness extraction in this framework, by discussing several
techniques depending on the shape of the existential formula. In particular, we
show that in the Sigma01-case, Krivine's witness extraction method reduces to
Friedman's through a well-suited negative translation to intuitionistic
second-order arithmetic. Finally we discuss the advantages of using call/cc
rather than a negative translation, especially from the point of view of an
implementation.Comment: 52 pages. Accepted in Logical Methods for Computer Science (LMCS),
201
Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences
The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & NemĂ©sio 2007; Donegan 2008, 2009; NemĂ©sio 2009aâb; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported
by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on
18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based
researchers who signed it in the short time span from 20 September to 6 October 2016
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Updating the approaches to define susceptibility and resistance to anti-tuberculosis agents: implications for diagnosis and treatment
11 pĂĄginas, 2 figuras, 1 tablaInappropriately high breakpoints have resulted in systematic false-susceptible AST results to anti-TB drugs. MIC, PK/PD and clinical outcome data should be combined when setting breakpoints to minimise the emergence and spread of antimicrobial resistance.I. Comas was supported by PID2019-104477RB-I00 from the Spanish Science Ministry
and by ERC (CoG 101001038)Peer reviewe