11,408 research outputs found
The missing top of AdS resonance structure
We study a massless scalar field in AdS_{d+1} with a nonlinear coupling
\phi^N and not limited to spherical symmetry. The free-field-eigenstate
spectrum is strongly resonant, and it is commonly believed that the nonlinear
coupling leads to energy transfer between eigenstates. We prove that when
is even, the most efficient resonant channels to transfer energy are always
absent. In particular, for N=3 this means no energy transfer at all. For N=4,
this effectively kills half of the channels, leading to the same set of extra
conservation laws recently derived for gravitational interactions within
spherical symmetry.Comment: 12 pages, no figures, version 2 that mutes "showkeys" correctly and
added one referenc
Conditionally Extended Validity of Perturbation Theory: Persistence of AdS Stability Islands
Approximating nonlinear dynamics with a truncated perturbative expan- sion
may be accurate for a while, but it in general breaks down at a long time scale
that is one over the small expansion parameter. There are interesting occasions
in which such breakdown does not happen. We provide a mathematically general
and precise definition of those occasions, in which we prove that the validity
of truncated theory trivially extends to the long time scale. This enables us
to utilize numerical results, which are only obtainable within finite times, to
legitimately predict the dynamic when the expansion parameter goes to zero,
thus the long time scale goes to infinity. In particular, this shows that
existing non-collapsing solutions in the AdS (in)stability problem persist to
the zero-amplitude limit, opposing the conjecture by Dias, Horowitz, Marolf and
Santos that predicts a shrinkage to measure-zero [1]. We also point out why the
persistence of collapsing solutions is harder to prove, and how the recent
interesting progress by Bizon, Maliborski and Rostoworowski is not there yet
[2].Comment: 19 pages, 1 figure, V2: Resubmitted to match the journal versio
Complementarity + Back-reaction is enough
We investigate a recent development of the black hole information problem, in
which a practical paradox has been formulated to show that complementarity is
insufficient. A crucial ingredient in this practical paradox is to distill
information from the early Hawking radiation within the past lightcone of the
black hole. By causality this action can back-react on the black hole. Taking
this back-reaction into account, the paradox could be resolved without invoking
any new physics beyond complementarity. This resolution requires a certain
constraint on the S-matrix to be satisfied. Further insights into the S-matrix
could potentially be obtained by effective-field-theory computations of the
back-reaction on the nice slice.Comment: v2, 21 pages, 4 figure
The Strong Multifield Slowroll Condition and Spiral Inflation
We point out the existing confusions about the slowroll parameters and
conditions for multifield inflation. If one requires the fields to roll down
the gradient flow, we find that only articles adopting the Hubble slowroll
expansion are on the right track, and a correct condition can be found in a
recent book by Liddle and Lyth. We further analyze this condition and show that
the gradient flow requirement is stronger than just asking for a slowly
changing, quasi-de Sitter solution. Therefore it is possible to have a
multifield slowroll model that does not follow the gradient flow. Consequently,
it no longer requires the gradient to be small. It even bypasses the first
slowroll condition and some related no-go theorems from string theory. We
provide the "spiral inflation" as a generic blueprint of such inflation model
and show that it relies on a monodromy locus---a common structure in string
theory effective potentials.Comment: 12 pages, version 4, cosmetic changes recommended by referee,
resubmitting to PR
Escaping the crunch: gravitational effects in classical transitions
During eternal inflation, a landscape of vacua can be populated by the
nucleation of bubbles. These bubbles inevitably collide, and collisions
sometimes displace the field into a new minimum in a process known as a
classical transition. In this paper, we examine some new features of classical
transitions that arise when gravitational effects are included. Using the
junction condition formalism, we study the conditions for energy conservation
in detail, and solve explicitly for the types of allowed classical transition
geometries. We show that the repulsive nature of domain walls, and the de
Sitter expansion associated with a positive energy minimum, can allow for
classical transitions to vacua of higher energy than that of the colliding
bubbles. Transitions can be made out of negative or zero energy (terminal)
vacua to a de Sitter phase, re-starting eternal inflation, and populating new
vacua. However, the classical transition cannot produce vacua with energy
higher than the original parent vacuum, which agrees with previous results on
the construction of pockets of false vacuum. We briefly comment on the possible
implications of these results for various measure proposals in eternal
inflation.Comment: 21 pages, 10 figure
Probability of Slowroll Inflation in the Multiverse
Slowroll after tunneling is a crucial step in one popular framework of the
multiverse---false vacuum eternal inflation (FVEI). In a landscape with a large
number of fields, we provide a heuristic estimation for its probability. We
find that the chance to slowroll is exponentially suppressed, where the
exponent comes from the number of fields. However, the relative probability to
have more e-foldings is only mildly suppressed as with
. Base on these two properties, we show that the FVEI picture is
still self-consistent and may have a strong preference between different
slowroll models.Comment: version 3, 21 pages, resubmit to PRD recommanded by refere
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