18,848 research outputs found
Heavy Thresholds, Slepton Masses and the Term in Anomaly Mediated Supersymmetry Breaking
The effects of heavy mass thresholds on anomaly-mediated soft supersymmetry
breaking terms are discussed. While heavy thresholds completely decouple to
lowest order in the supersymmetry breaking, it is argued that they do affect
the breaking terms at higher orders. The relevant contributions typically occur
at lower order in the loop expansion compared to purely anomaly mediated
contributions. The non decoupling contributions may be used to render models in
which the only source of supersymmetry breaking is anomaly mediation viable, by
generating positive contributions to the sleptons' masses squared. They can
also be used to generate acceptable mu- and B-terms.Comment: 25 pages, late
Effects of aminoperimidine on electrolyte transport across amphibian skin
The effect of aminoperimidine (AP)on transepithelial Na+ transport and Cl- conductance (G(Cl)) of isolated amphibian skin (Bufo viridis and Rana esculenta) was analyzed using transepithelial and intracellular electrophysiological techniques. AP, applied at concentrations between 30 and 100 mu M from the mucosal side, stimulated Na+ transport rapidly and reversibly by more than 30% of the control value due to an increase in apical membrane Na+ permeability. Influence of AP on basolateral membrane conductance and effective driving force for Na+ were negligible. Voltage-activated G(Cl) of toad skin, but not the resting, deactivated conductance, as well as spontaneously high G(Cl) in frog skin was rapidly inhibited by AP in a concentration-dependent manner. The half-maximal inhibitory concentration of 20 mu M is the highest hithero reported inhibitory power for G(Cl) in amphibian skin. The effect of AP on G(Cl) was slowly and incompletely reversible even after brief exposure to the agent. Serosal application of AP had similar, albeit delayed effects on both Nai and Cl- transport. AP did not interfere with the Cl- pathway after it was opened by 100-300 mu M CPT-cAMP, a membrane-permeable, nonhydrolyzed analogue of cAMP. Inhibition of the voltage-activated G(Cl) by AP was attenuated or missing when AP was applied during voltage perturbation to serosa-positive potentials. Since AP is positively charged at physiological pH, it suggests that the affected site is located inside the Cl- pathway at a certain distance from the external surface. AP affects then the Na+ and Cl- transport pathways independent of each other. The nature of chemical interference with AP, which is responsible for the influence on the transport of Na+ and Cl-, remains to be elucidated
On satellite meteorology studies Final report
Satellite meteorology research on polar energy budget, atmospherics detection, and Mars atmospheric circulatio
A multi-method approach to radial-velocity measurement for single-object spectra
The derivation of radial velocities from large numbers of spectra that
typically result from survey work, requires automation. However, except for the
classical cases of slowly rotating late-type spectra, existing methods of
measuring Doppler shifts require fine-tuning to avoid a loss of accuracy due to
the idiosyncrasies of individual spectra. The radial velocity spectrometer
(RVS) on the Gaia mission, which will start operating very soon, prompted a new
attempt at creating a measurement pipeline to handle a wide variety of spectral
types.
The present paper describes the theoretical background on which this software
is based. However, apart from the assumption that only synthetic templates are
used, we do not rely on any of the characteristics of this instrument, so our
results should be relevant for most telescope-detector combinations.
We propose an approach based on the simultaneous use of several alternative
measurement methods, each having its own merits and drawbacks, and conveying
the spectral information in a different way, leading to different values for
the measurement. A comparison or a combination of the various results either
leads to a "best estimate" or indicates to the user that the observed spectrum
is problematic and should be analysed manually.
We selected three methods and analysed the relationships and differences
between them from a unified point of view; with each method an appropriate
estimator for the individual random error is chosen. We also develop a
procedure for tackling the problem of template mismatch in a systematic way.
Furthermore, we propose several tests for studying and comparing the
performance of the various methods as a function of the atmospheric parameters
of the observed objects. Finally, we describe a procedure for obtaining a
knowledge-based combination of the various Doppler-shift measurements.Comment: 16 pages, 4 figure
Accurate determination of the Lagrangian bias for the dark matter halos
We use a new method, the cross power spectrum between the linear density
field and the halo number density field, to measure the Lagrangian bias for
dark matter halos. The method has several important advantages over the
conventional correlation function analysis. By applying this method to a set of
high-resolution simulations of 256^3 particles, we have accurately determined
the Lagrangian bias, over 4 magnitudes in halo mass, for four scale-free models
with the index n=-0.5, -1.0, -1.5 and -2.0 and three typical CDM models. Our
result for massive halos with ( is a characteristic non-linear
mass) is in very good agreement with the analytical formula of Mo & White for
the Lagrangian bias, but the analytical formula significantly underestimates
the Lagrangian clustering for the less massive halos $M < M_*. Our simulation
result however can be satisfactorily described, with an accuracy better than
15%, by the fitting formula of Jing for Eulerian bias under the assumption that
the Lagrangian clustering and the Eulerian clustering are related with a linear
mapping. It implies that it is the failure of the Press-Schechter theories for
describing the formation of small halos that leads to the inaccuracy of the Mo
& White formula for the Eulerian bias. The non-linear mapping between the
Lagrangian clustering and the Eulerian clustering, which was speculated as
another possible cause for the inaccuracy of the Mo & White formula, must at
most have a second-order effect. Our result indicates that the halo formation
model adopted by the Press-Schechter theories must be improved.Comment: Minor changes; accepted for publication in ApJ (Letters) ; 11 pages
with 2 figures include
Quantum Fully Homomorphic Encryption With Verification
Fully-homomorphic encryption (FHE) enables computation on encrypted data
while maintaining secrecy. Recent research has shown that such schemes exist
even for quantum computation. Given the numerous applications of classical FHE
(zero-knowledge proofs, secure two-party computation, obfuscation, etc.) it is
reasonable to hope that quantum FHE (or QFHE) will lead to many new results in
the quantum setting. However, a crucial ingredient in almost all applications
of FHE is circuit verification. Classically, verification is performed by
checking a transcript of the homomorphic computation. Quantumly, this strategy
is impossible due to no-cloning. This leads to an important open question: can
quantum computations be delegated and verified in a non-interactive manner? In
this work, we answer this question in the affirmative, by constructing a scheme
for QFHE with verification (vQFHE). Our scheme provides authenticated
encryption, and enables arbitrary polynomial-time quantum computations without
the need of interaction between client and server. Verification is almost
entirely classical; for computations that start and end with classical states,
it is completely classical. As a first application, we show how to construct
quantum one-time programs from classical one-time programs and vQFHE.Comment: 30 page
Analytic understanding of the resonant nature of Kozai Lidov Cycles with a precessing quadruple potential
The very long-term evolution of the hierarchical restricted three-body
problem with a precessing quadruple potential is studied analytically. This
problem describes the evolution of a star and a planet which are perturbed
either by a (circular and not too inclined) binary star system or by one other
star and a second more distant star, as well as a perturbation by one distant
star and the host galaxy or a compact-object binary system orbiting a massive
black hole in non-spherical nuclear star clusters \citep{arXiv:1705.02334v2,
arXiv:1705.05848v2}. Previous numerical experiments have shown that when the
precession frequency is comparable to the Kozai-Lidov time scale, long term
evolution emerges that involves extremely high eccentricities with potential
applications for a broad scope of astrophysical phenomena including systems
with merging black holes, neutron stars or white dwarfs. We show that a central
ingredient of the dynamics is a resonance between the perturbation frequency
and the precession frequency of the eccentricity vector in the regime where the
eccentricity vector, the precession axis and the quadruple direction are
closely aligned. By averaging the secular equations of motion over the
Kozai-Lidov Cycles we solve the problem analytically in this regime.Comment: 5 pages, 2 figure
The QCD transition temperature: results with physical masses in the continuum limit
The transition temperature () of QCD is determined by Symanzik improved
gauge and stout-link improved staggered fermionic lattice simulations. We use
physical masses both for the light quarks () and for the strange quark
(). Four sets of lattice spacings (=4,6,8 and 10) were used to carry
out a continuum extrapolation. It turned out that only =6,8 and 10 can be
used for a controlled extrapolation, =4 is out of the scaling region.
Since the QCD transition is a non-singular cross-over there is no unique .
Thus, different observables lead to different numerical values even in
the continuum and thermodynamic limit. The peak of the renormalized chiral
susceptibility predicts =151(3)(3) MeV, wheres -s based on the
strange quark number susceptibility and Polyakov loops result in 24(4) MeV and
25(4) MeV larger values, respectively. Another consequence of the cross-over is
the non-vanishing width of the peaks even in the thermodynamic limit, which we
also determine. These numbers are attempted to be the full result for the
0 transition, though other lattice fermion formulations (e.g. Wilson)
are needed to cross-check them.Comment: 13 pages 5 figures. Final version, published in Phys.Lett.
Feature-Guided Black-Box Safety Testing of Deep Neural Networks
Despite the improved accuracy of deep neural networks, the discovery of
adversarial examples has raised serious safety concerns. Most existing
approaches for crafting adversarial examples necessitate some knowledge
(architecture, parameters, etc.) of the network at hand. In this paper, we
focus on image classifiers and propose a feature-guided black-box approach to
test the safety of deep neural networks that requires no such knowledge. Our
algorithm employs object detection techniques such as SIFT (Scale Invariant
Feature Transform) to extract features from an image. These features are
converted into a mutable saliency distribution, where high probability is
assigned to pixels that affect the composition of the image with respect to the
human visual system. We formulate the crafting of adversarial examples as a
two-player turn-based stochastic game, where the first player's objective is to
minimise the distance to an adversarial example by manipulating the features,
and the second player can be cooperative, adversarial, or random. We show that,
theoretically, the two-player game can con- verge to the optimal strategy, and
that the optimal strategy represents a globally minimal adversarial image. For
Lipschitz networks, we also identify conditions that provide safety guarantees
that no adversarial examples exist. Using Monte Carlo tree search we gradually
explore the game state space to search for adversarial examples. Our
experiments show that, despite the black-box setting, manipulations guided by a
perception-based saliency distribution are competitive with state-of-the-art
methods that rely on white-box saliency matrices or sophisticated optimization
procedures. Finally, we show how our method can be used to evaluate robustness
of neural networks in safety-critical applications such as traffic sign
recognition in self-driving cars.Comment: 35 pages, 5 tables, 23 figure
Cosmic ray modulation in a random anisotropic magnetic field
Inhomogeneities of the interplanetary magnetic field can be divided into small scale and large scale ones as may be required by the character of the problem of cosmic ray (CR) propagation. CR propagation in stochastic magnetic fields is of diffusion character. The main contribution into the scattering of CR particles is made by their interaction with inhomogeneities of the magnetic field H which have characteristic dimensions 1 of the order of Larmor radius R=cp/eH of particle (p is the absolute value of particle momentum, e is particle charge, c is velocity of light). Scattering of particles on such inhomogeneities leads to their diffusion mostly along a magnetic field with characteristic dimensions of variation in space exceeding the mean free path
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