248 research outputs found
Addendum to Fast Scramblers
This paper is an addendum to [arXiv:0808.2096] in which I point out that both
de Sitter space and Rindler space are fast scramblers. This fact naturally
suggests that the holographic description of a causal patch of de Sitter space
may be a matrix quantum mechanics at finite temperature. The same can be said
of Rindler space. Some qualitative features of these spaces can be understood
from the matrix description.Comment: 16 pages, 2 figure
Cosmic Natural Selection
I make a number of comments about Smolin's theory of Cosmic Natural
Selection
Rebuttal to a Paper on Wormholes
In a recent paper on wormholes (gr-qc/0503097), the author of that paper
demonstrated that he didn't know what he was talking about. In this paper I
correct the author's naive erroneous misconceptions
Fractal-Flows and Time's Arrow
This is the written version of a lecture at the KITP workshop on Bits,
Branes, and Black Holes. In it I describe work with D. Harlow, S. Shenker, D.
Stanford which explains how the tree-like structure of eternal inflation,
together with the existence of terminal vacua, leads to an arrow-of-time.
Conformal symmetry of the dS/CFT type is inconsistent with an arrow-of-time and
must be broken. The presence in the landscape of terminal vacua leads to a new
kind of attractor called a fractal-flow, which both breaks conformal symmetry,
and creates a directional time-asymmetry. This can be seen from both the local
or causal-patch viewpoint, and also from the global or multiversal viewpoint.
The resulting picture is consistent with the view recently expressed by Bousso.
In the last part of the lecture I illustrate how the tree-model can be useful
in explaining the value of the cosmological constant and the cosmic coincidence
problem. The mechanisms are not new but the description is.Comment: 24 pages, 5 figure
Is Eternal Inflation Past-Eternal? And What if It Is?
As a result of discussions with Bousso and Vilenkin I want to return to the
question of whether the multiverse is past-eternal or if there was a beginning.
Not surprisingly, given three people, there were three answers. However, the
discussions have led to some common ground.
The multiverse being past-eternal, or at least extremely old has content and
potential phenomenological implications. I will discuss how the oldness of the
multiverse is connected with recent speculations of Douglas.Comment: 13 pages, 4 figure
Addendum to Computational Complexity and Black Hole Horizons
In this addendum to [arXiv:1402.5674] two points are discussed. In the first
additional evidence is provided for a dual connection between the geometric
length of an Einstein-Rosen bridge and the computational complexity of the
quantum state of the dual CFT's. The relation between growth of complexity and
Page's ``Extreme Cosmic Censorship" principle is also remarked on.
The second point involves a gedanken experiment in which Alice measures a
complete set of commuting observables at her end of an Einstein-Rosen bridge is
discussed. An apparent paradox is resolved by appealing to the properties of
GHZ tripartite entanglement.Comment: 11 pages, 1 figur
PiTP Lectures on Complexity and Black Holes
This is the first of three PiTP lectures on complexity and its role in black
hole physics.Comment: Lectures, PiTP summer school, 2018. Superseded by arXiv:1810.1156
Singularities, Firewalls, and Complementarity
Almheiri, Marolf, Polchinski, and Sully, recently claimed that once a black
hole has radiated more than half its initial entropy (the Page time), the
horizon is replaced by a "firewall" at which infalling observers burn up, in
apparent violation of the equivalence principle and the postulates of black
hole complementarity. In this paper I review the arguments for firewalls, and
give a slightly different interpretation of them. According to this
interpretation the horizon has standard properties, but the singularity is
non-standard. The growing entanglement of the black hole with Hawking radiation
causes the singularity to migrate toward the horizon, and eventually intersect
it at the page time. The resulting collision of the singularity with the
horizon leads to the firewall. Complementarity applies to the horizon and not
to the singular firewall.
Almheiri, Marolf, Polchinski, and Sully conjecture that firewalls form much
earlier then the Page time; namely at the scrambling time. I argue that there
is no reason to believe this generalization, and good reason to think it is
wrong.
For most of this paper I will assume that the firewall argument is correct.
In the last section before the conclusion I will describe reasons for having
reservations.Comment: 28 pages, 8 figure
Complexity and Newton's Laws
In a recent note I argued that the holographic origin of gravitational
attraction is the quantum mechanical tendency for operators to grow under time
evolution. In a followup the claim was tested in the context of the SYK theory
and its bulk dual---the theory of near-extremal black holes. In this paper I
give an improved version of the size-momentum correspondence and show that
Newton's laws of motion are a consequence. Operator size is closely related to
complexity. Therefore one may say that gravitational attraction is a
manifestation of the tendency for complexity to increase.
The improved version of the size-momentum correspondence can be justified by
the arguments of Lin, Maldacena, and Zhao constructing symmetry generators for
the approximate symmetries of the SYK model.Comment: 13 figure
Was There a Beginning?
In this note I respond to Vilenkin's claim that there must have been a
beginning.Comment: 4 pages, 2 figure
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