158 research outputs found
Bitcoin Crypto - bounties for quantum capable adversaries
With the advances in quantum computing taking place over the last few years, researchers have started considering the implications on cryptocurrencies. As most digital signature schemes would be impacted, it is somewhat reassuring that transition schemes to quantum resistant signatures are already being considered for Bitcoin. In this work, we stress the danger of public key reuse, as it prevents users from recovering their funds in the presence of a quantum enabled adversary despite any transition scheme the developers decide to implement. We emphasize this threat by quantifying the damage a functional quantum computer could inflict on Bitcoin (and Bitcoin Cash) by breaking exposed public keys
Using subthreshold events to characterize the functional architecture of the electrically coupled inferior olive network
The electrical connectivity in the inferior olive (IO) nucleus plays an important role in generating well-timed spiking activity. Here we combined electrophysiological and computational approaches to assess the functional organization of the IO nucleus in mice. Spontaneous fast and slow subthreshold events were commonly encountered during in vitro recordings. We show that whereas the fast events represent intrinsic regenerative activity, the slow events reflect the electrical connectivity between neurons ('spikelets'). Recordings from cell pairs revealed the synchronized occurrence of distinct groups of spikelets; their rate and distribution enabled an accurate estimation of the number of connected cells and is suggestive of a clustered organization. This study thus provides a new perspective on the functional and structural organization of the olivary nucleus and a novel experimental and theoretical approach to study electrically coupled networks
CD74 (CD74 molecule, major histocompatibility complex, class II invariant chain)
Review on CD74, with data on DNA/RNA, on the protein encoded and where the gene is implicated
Synchronous Behavior of Two Coupled Electronic Neurons
We report on experimental studies of synchronization phenomena in a pair of
analog electronic neurons (ENs). The ENs were designed to reproduce the
observed membrane voltage oscillations of isolated biological neurons from the
stomatogastric ganglion of the California spiny lobster Panulirus interruptus.
The ENs are simple analog circuits which integrate four dimensional
differential equations representing fast and slow subcellular mechanisms that
produce the characteristic regular/chaotic spiking-bursting behavior of these
cells. In this paper we study their dynamical behavior as we couple them in the
same configurations as we have done for their counterpart biological neurons.
The interconnections we use for these neural oscillators are both direct
electrical connections and excitatory and inhibitory chemical connections: each
realized by analog circuitry and suggested by biological examples. We provide
here quantitative evidence that the ENs and the biological neurons behave
similarly when coupled in the same manner. They each display well defined
bifurcations in their mutual synchronization and regularization. We report
briefly on an experiment on coupled biological neurons and four dimensional ENs
which provides further ground for testing the validity of our numerical and
electronic models of individual neural behavior. Our experiments as a whole
present interesting new examples of regularization and synchronization in
coupled nonlinear oscillators.Comment: 26 pages, 10 figure
Scanning the Parameter Space of Holographic Superconductors
We study various physical quantities associated with holographic s-wave
superconductors as functions of the scaling dimensions of the dual condensates.
A bulk scalar field with negative mass squared , satisfying the
Breitenlohner-Freedman stability bound and the unitarity bound, and allowed to
vary in unit intervals, were considered. We observe that all the physical
quantities investigated are sensitive to the scaling dimensions of the dual
condensates. For all the , the characteristic lengths diverge at the
critical temperature in agreement with the Ginzburg-Landau theory. The
Ginzburg-Landau parameter, obtained from these length scales indicates that the
holographic superconductors can be type I or type II depending on the charge
and the scaling dimensions of the dual condensates. For a fixed charge, there
exists a critical scaling dimension, above which a holographic superconductor
is type I, below which it becomes a type II.Comment: 24 pages 47 figure
Short distance properties of cascading gauge theories
We study the short distance (large momentum) properties of correlation
functions of cascading gauge theories by performing a tree-level computation in
their dual gravitational background. We prove that these theories are
holographically renormalizable; the correlators have only analytic ultraviolet
divergences, which may be removed by appropriate local counterterms. We find
that n-point correlation functions of properly normalized operators have the
expected scaling in the semi-classical gravity (large N) limit: they scale as
N_{eff}^{2-n} with N_{eff} proportional to ln(k/Lambda) where k is a typical
momentum. Our analysis thus confirms the interpretation of the cascading gauge
theories as renormalizable four-dimensional quantum field theories with an
effective number of degrees of freedom which logarithmically increases with the
energy.Comment: 47 pages, no figure
Absence of a Fermi surface in classical minimal four-dimensional gauged supergravity
We demonstrate that the two point function of the supercurrent dual to the
gravitino in the four-dimensional extremal anti-de Sitter Reissner-Nordstrom
black hole does not exhibit a Fermi surface singularity. In our analysis, we
utilize the ingoing Eddington-Finkelstein coordinate system, which enables us
to bypass certain complications in the determination of the allowed near
horizon behavior of the gravitino field at zero frequency. We check that our
method agrees with previous results for the massless charged Dirac field.Comment: 12 pages, 1 figur
An elementary stringy estimate of transport coefficients of large temperature QCD
Modeling QCD at large temperature with a simple holographic five dimensional
theory encoding minimal breaking of conformality, allows for the calculation of
all the transport coefficients, up to second order, in terms of a single
parameter. In particular, the shear and bulk relaxation times are provided. The
result follows by deforming the AdS background with a scalar dual to a
marginally relevant operator, at leading order in the deformation parameter.Comment: 11 pages; v2: comments and references adde
The Gluonic Field of a Heavy Quark in Conformal Field Theories at Strong Coupling
We determine the gluonic field configuration sourced by a heavy quark
undergoing arbitrary motion in N=4 super-Yang-Mills at strong coupling and
large number of colors. More specifically, we compute the expectation value of
the operator tr[F^2+...] in the presence of such a quark, by means of the
AdS/CFT correspondence. Our results for this observable show that signals
propagate without temporal broadening, just as was found for the expectation
value of the energy density in recent work by Hatta et al. We attempt to shed
some additional light on the origin of this feature, and propose a different
interpretation for its physical significance. As an application of our general
results, we examine when the quark undergoes oscillatory motion,
uniform circular motion, and uniform acceleration. Via the AdS/CFT
correspondence, all of our results are pertinent to any conformal field theory
in 3+1 dimensions with a dual gravity formulation.Comment: 1+38 pages, 16 eps figures; v2: completed affiliation; v3: corrected
typo, version to appear in JHE
Transport in holographic superfluids
We construct a slowly varying space-time dependent holographic superfluid and
compute its transport coefficients. Our solution is presented as a series
expansion in inverse powers of the charge of the order parameter. We find that
the shear viscosity associated with the motion of the condensate vanishes. The
diffusion coefficient of the superfluid is continuous across the phase
transition while its third bulk viscosity is found to diverge at the critical
temperature. As was previously shown, the ratio of the shear viscosity of the
normal component to the entropy density is 1/(4 pi). As a consequence of our
analysis we obtain an analytic expression for the backreacted metric near the
phase transition for a particular type of holographic superfluid.Comment: 45 pages + appendice
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