11,677 research outputs found
Dynamics for holographic codes
We describe how to introduce dynamics for the holographic states and codes
introduced by Pastawski, Yoshida, Harlow and Preskill. This task requires the
definition of a continuous limit of the kinematical Hilbert space which we
argue may be achieved via the semicontinuous limit of Jones. Dynamics is then
introduced by building a unitary representation of a group known as Thompson's
group T, which is closely related to the conformal group in 1+1 dimensions. The
bulk Hilbert space is realised as a special subspace of the semicontinuous
limit Hilbert space spanned by a class of distinguished states which can be
assigned a discrete bulk geometry. The analogue of the group of large bulk
diffeomorphisms is given by a unitary representation of the Ptolemy group Pt,
on the bulk Hilbert space thus realising a toy model of the AdS/CFT
correspondence which we call the Pt/T correspondence.Comment: 40 pages (revised version submitted to journal). See video of related
talk: https://www.youtube.com/watch?v=xc2KIa2LDF
Limited phase deviation frequency multiplier phase modulator, appendix e final report
Limited phase deviation frequency multiplier phase modulator - application to radio frequency test console equipmen
Quantum phases of a chain of strongly interacting anyons
We study a strongly interacting chain of anyons with fusion rules determined
by SO(5)2. The phase portrait is identified with a combination of numerical and
analytical techniques. Several critical phases with different central charges
and their corresponding transitions identified.Comment: 5 pages, 4 figure
Resumption of mass accretion in RS Oph
The latest outburst of the recurrent nova RS Oph occurred in 2006 February. Photometric data presented here show evidence of the resumption of optical flickering, indicating re-establishment of accretion by day 241 of the outburst. Magnitude variations of up to 0.32 mag in V band and 0.14 mag in B band on time-scales of 600â7000 s are detected. Over the two-week observational period, we also detect a 0.5 mag decline in the mean brightness, from Vâ 11.4 to 11.9, and record Bâ 12.9 mag. Limits on the mass accretion rate of [inline image] are calculated, which span the range of accretion rates modelled for direct wind accretion and Roche lobe overflow mechanisms. The current accretion rates make it difficult for thermonuclear runaway models to explain the observed recurrence interval, and this implies average accretion rates are typically higher than seen immediately post-outburst
General Monogamy Inequality for Bipartite Qubit Entanglement
We consider multipartite states of qubits and prove that their bipartite
quantum entanglement, as quantified by the concurrence, satisfies a monogamy
inequality conjectured by Coffman, Kundu, and Wootters. We relate this monogamy
inequality to the concept of frustration of correlations in quantum spin
systems.Comment: Fixed spelling mistake. Added references. Fixed error in
transformation law. Shorter and more explicit proof of capacity formula.
Reference added. Rewritten introduction and conclusion
The SSS phase of RS Ophiuchi observed with Chandra and XMM-Newton I.: Data and preliminary Modeling
The phase of Super-Soft-Source (SSS) emission of the sixth recorded outburst
of the recurrent nova RS Oph was observed twice with Chandra and once with
XMM-Newton. The observations were taken on days 39.7, 54.0, and 66.9 after
outburst. We confirm a 35-sec period on day 54.0 and found that it originates
from the SSS emission and not from the shock. We discus the bound-free
absorption by neutral elements in the line of sight, resonance absorption lines
plus self-absorbed emission line components, collisionally excited emission
lines from the shock, He-like intersystem lines, and spectral changes during an
episode of high-amplitude variability. We find a decrease of the oxygen K-shell
absorption edge that can be explained by photoionization of oxygen. The
absorption component has average velocities of -1286+-267 km/s on day 39.7 and
of -771+-65 km/s on day 66.9. The wavelengths of the emission line components
are consistent with their rest wavelengths as confirmed by measurements of
non-self absorbed He-like intersystem lines. We have evidence that these lines
originate from the shock rather than the outer layers of the outflow and may be
photoexcited in addition to collisional excitations. We found collisionally
excited emission lines that are fading at wavelengths shorter than 15A that
originate from the radiatively cooling shock. On day 39.5 we find a systematic
blue shift of -526+-114 km/s from these lines. We found anomalous He-like f/i
ratios which indicates either high densities or significant UV radiation near
the plasma where the emission lines are formed. During the phase of strong
variability the spectral hardness light curve overlies the total light curve
when shifted by 1000sec. This can be explained by photoionization of neutral
oxygen in the line of sight if the densities of order 10^{10}-10^{11} cm^{-3}.Comment: 16 pages, 10 figures, 4 tables. Accepted by ApJ; v2: Co-author
Woodward adde
Causal structure of the entanglement renormalization ansatz
We show that the multiscale entanglement renormalization ansatz (MERA) can be
reformulated in terms of a causality constraint on discrete quantum dynamics.
This causal structure is that of de Sitter space with a flat spacelike
boundary, where the volume of a spacetime region corresponds to the number of
variational parameters it contains. This result clarifies the nature of the
ansatz, and suggests a generalization to quantum field theory. It also
constitutes an independent justification of the connection between MERA and
hyperbolic geometry which was proposed as a concrete implementation of the
AdS-CFT correspondence
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