3,677 research outputs found
Lattice QCD with domain wall quarks and applications to weak matrix elements
Using domain wall fermions, we estimate in
quenched QCD which is consistent with previous calculations. At \gbeta=6.0
and 5.85 we find the ratio in agreement with the experimental
value, within errors. These results support expectations that errors are
exponentially suppressed in low energy () observables, and
indicate that domain wall fermions have good scaling behavior at relatively
strong couplings. We also demonstrate that the axial current numerically
satisfies the lattice analog of the usual continuum axial Ward identity.Comment: Contribution to Lattice '97. 3 pages, 2 epsf figure
OT 060420: A Seemingly Optical Transient Recorded by All-Sky Cameras
We report on a ~5th magnitude flash detected for approximately 10 minutes by
two CONCAM all-sky cameras located in Cerro Pachon - Chile and La Palma -
Spain. A third all-sky camera, located in Cerro Paranal - Chile did not detect
the flash, and therefore the authors of this paper suggest that the flash was a
series of cosmic-ray hits, meteors, or satellite glints. Another proposed
hypothesis is that the flash was an astronomical transient with variable
luminosity. In this paper we discuss bright optical transient detection using
fish-eye all-sky monitors, analyze the apparently false-positive optical
transient, and propose possible causes to false optical transient detection in
all-sky cameras.Comment: 7 figures, 3 tables, accepted PAS
Using secret sharing for searching in encrypted data
When outsourcing data to an untrusted database server, the data should be encrypted. When using thin clients or low-bandwidth networks it is best to perform most of the work at the server. We present a method, inspired by secure multi-party computation, to search efficiently in encrypted data. XML elements are translated to polynomials. A polynomial is split into two parts: a random polynomial for the client and the difference between the original polynomial and the client polynomial for the server. Since the client polynomials are generated by a random sequence generator only the seed has to be stored on the client. In a combined effort of both the server and the client a query can be evaluated without traversing the whole tree and without the server learning anything about the data or the query
The role of the double pole in lattice QCD with mixed actions
We investigate effects resulting from the use of different discretizations
for the valence and the sea quarks in lattice QCD, considering Wilson and/or
Ginsparg-Wilson fermions. We assume that such effects appear through scaling
violations that can be studied using effective lagrangian techniques. We show
that a double pole is present in flavor-neutral Goldstone meson
propagators,even if the charged Goldstone mesons made out of valence quarks and
those made out of sea quarks have equal masses. We then consider some
observables known to be anomalously sensitive to the presence of a double pole.
For these observables, we find that the double-pole enhanced scaling violations
may turn out to be rather small in practice.Comment: 13 page
Fourier-based Function Secret Sharing with General Access Structure
Function secret sharing (FSS) scheme is a mechanism that calculates a
function f(x) for x in {0,1}^n which is shared among p parties, by using
distributed functions f_i:{0,1}^n -> G, where G is an Abelian group, while the
function f:{0,1}^n -> G is kept secret to the parties. Ohsawa et al. in 2017
observed that any function f can be described as a linear combination of the
basis functions by regarding the function space as a vector space of dimension
2^n and gave new FSS schemes based on the Fourier basis. All existing FSS
schemes are of (p,p)-threshold type. That is, to compute f(x), we have to
collect f_i(x) for all the distributed functions. In this paper, as in the
secret sharing schemes, we consider FSS schemes with any general access
structure. To do this, we observe that Fourier-based FSS schemes by Ohsawa et
al. are compatible with linear secret sharing scheme. By incorporating the
techniques of linear secret sharing with any general access structure into the
Fourier-based FSS schemes, we show Fourier-based FSS schemes with any general
access structure.Comment: 12 page
Robust Coin Flipping
Alice seeks an information-theoretically secure source of private random
data. Unfortunately, she lacks a personal source and must use remote sources
controlled by other parties. Alice wants to simulate a coin flip of specified
bias , as a function of data she receives from sources; she seeks
privacy from any coalition of of them. We show: If , the
bias can be any rational number and nothing else; if , the bias
can be any algebraic number and nothing else. The proof uses projective
varieties, convex geometry, and the probabilistic method. Our results improve
on those laid out by Yao, who asserts one direction of the case in his
seminal paper [Yao82]. We also provide an application to secure multiparty
computation.Comment: 22 pages, 1 figur
Localization properties of lattice fermions with plaquette and improved gauge actions
We determine the location of the mobility edge in the spectrum of
the hermitian Wilson operator in pure-gauge ensembles with plaquette, Iwasaki,
and DBW2 gauge actions. The results allow mapping a portion of the (quenched)
Aoki phase diagram. We use Green function techniques to study the localized and
extended modes. Where we characterize the localized modes in
terms of an average support length and an average localization length, the
latter determined from the asymptotic decay rate of the mode density. We argue
that, since the overlap operator is commonly constructed from the Wilson
operator, its range is set by the value of for the Wilson
operator. It follows from our numerical results that overlap simulations
carried out with a cutoff of 1 GeV, even with improved gauge actions, could be
afflicted by unphysical degrees of freedom as light as 250 MeV.Comment: RevTeX, 37 pages, 10 figures. Some textual changes. Final for
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