13,847 research outputs found
Ultraviolet Radiation from Evolved Stellar Populations: II. The Ultraviolet Upturn Phenomenon in Elliptical Galaxies
We present an analysis of the far-ultraviolet upturn phenomenon (UVX)
observed in elliptical galaxies and spiral galaxy bulges. Our premise is that
the UV radiation from these systems emanates primarily from extreme horizontal
branch (EHB) stars and their progeny. We re-derive the broad-band UV colors
and for globular clusters and elliptical galaxies from the
available satellite data and investigate color-color and color-line strength
correlations. We also provide the ingredients necessary for constructing models
with arbitrary HB morphologies.Comment: uuencoded compressed postscript file, 60pp. (revisions on pp.
7,8,22,33,37 & 57
Quantum computation with Turaev-Viro codes
The Turaev-Viro invariant for a closed 3-manifold is defined as the
contraction of a certain tensor network. The tensors correspond to tetrahedra
in a triangulation of the manifold, with values determined by a fixed spherical
category. For a manifold with boundary, the tensor network has free indices
that can be associated to qudits, and its contraction gives the coefficients of
a quantum error-correcting code. The code has local stabilizers determined by
Levin and Wen. For example, applied to the genus-one handlebody using the Z_2
category, this construction yields the well-known toric code.
For other categories, such as the Fibonacci category, the construction
realizes a non-abelian anyon model over a discrete lattice. By studying braid
group representations acting on equivalence classes of colored ribbon graphs
embedded in a punctured sphere, we identify the anyons, and give a simple
recipe for mapping fusion basis states of the doubled category to ribbon
graphs. We explain how suitable initial states can be prepared efficiently, how
to implement braids, by successively changing the triangulation using a fixed
five-qudit local unitary gate, and how to measure the topological charge.
Combined with known universality results for anyonic systems, this provides a
large family of schemes for quantum computation based on local deformations of
stabilizer codes. These schemes may serve as a starting point for developing
fault-tolerance schemes using continuous stabilizer measurements and active
error-correction.Comment: 53 pages, LaTeX + 199 eps figure
Precursors, Gauge Invariance, and Quantum Error Correction in AdS/CFT
A puzzling aspect of the AdS/CFT correspondence is that a single bulk
operator can be mapped to multiple different boundary operators, or precursors.
By improving upon a recent model of Mintun, Polchinski, and Rosenhaus, we
demonstrate explicitly how this ambiguity arises in a simple model of the field
theory. In particular, we show how gauge invariance in the boundary theory
manifests as a freedom in the smearing function used in the bulk-boundary
mapping, and explicitly show how this freedom can be used to localize the
precursor in different spatial regions. We also show how the ambiguity can be
understood in terms of quantum error correction, by appealing to the
entanglement present in the CFT. The concordance of these two approaches
suggests that gauge invariance and entanglement in the boundary field theory
are intimately connected to the reconstruction of local operators in the dual
spacetime.Comment: 25 pages, 6 figure
Magnetic field of superconductive in-vacuo undulators in comparison with permanent magnet undulators
During the last few years superconductive undulators with a period length of
3.8 mm and 14 mm have been built. In this paper scaling laws for these novel
insertion devices are presented: a simple analytic formula is derived which
describes the achievable magnetic field of a superconcuctive undulator as a
function of gap-width and period length.Comment: Accepted for publication in Nuclear Instruments and Methods in
Physics Research, Section
Vacuum energy sequestering and conformal symmetry
In a series of recent papers Kaloper and Padilla proposed a mechanism to
sequester standard model vacuum contributions to the cosmological constant. We
study the consequences of embedding their proposal into a fully local quantum
theory. In the original work, the bare cosmological constant and a
scaling parameter are introduced as global fields. We find that in
the local case the resulting Lagrangian is that of a spontaneously broken
conformal field theory where plays the role of the dilaton. A
vanishing or a small cosmological constant is thus a consequence of the
underlying conformal field theory structure.Comment: Extended discussion on the conformal symmetry. Matches the published
versio
Sub-AdS Scale Locality in AdS/CFT
We investigate sub-AdS scale locality in a weakly coupled toy model of the
AdS/CFT correspondence. We find that this simple model has the correct
density of states at low and high energies to be dual to Einstein gravity
coupled to matter in AdS. Bulk correlation functions also have the correct
behavior at leading order in the large expansion, but non-local effects
emerge at order . Our analysis leads to the conjecture that any large
CFT that is modular invariant and has the right low-energy density of
states is dual to a gravitational theory with sub-AdS scale locality.Comment: 19 page
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