7,931 research outputs found
Collider Inclusive Jet Data and the Gluon Distribution
Inclusive jet production data are important for constraining the gluon
distribution in the global QCD analysis of parton distribution functions. With
the addition of recent CDF and D0 Run II jet data, we study a number of issues
that play a role in determining the up-to-date gluon distribution and its
uncertainty, and produce a new set of parton distributions that make use of
that data. We present in detail the general procedures used to study the
compatibility between new data sets and the previous body of data used in a
global fit. We introduce a new method in which the Hessian matrix for
uncertainties is ``rediagonalized'' to obtain eigenvector sets that
conveniently characterize the uncertainty of a particular observable.Comment: Published versio
Quantum Entanglement of Moving Bodies
We study the properties of quantum information and quantum entanglement in
moving frames. We show that the entanglement between the spins and the momenta
of two particles can be interchanged under a Lorentz transformation, so that a
pair of particles that is entangled in spin but not momentum in one reference
frame, may, in another frame, be entangled in momentum at the expense of
spin-entanglement. Similarly, entanglement between momenta may be transferred
to spin under a Lorentz transformation. While spin and momentum entanglement
each is not Lorentz invariant, the joint entanglement of the wave function is.Comment: 4 pages, 2 figures. An error was corrected in the numerical data and
hence the discussion of the data was changed. Also, references were added.
Another example was added to the pape
Perturbation Calculation of the Axial Anomaly of a Ginsparg-Wilson lattice Dirac operator
A recent proposal suggests that even if a Ginsparg-Wilson lattice Dirac
operator does not possess any topological zero modes in
topologically-nontrivial gauge backgrounds, it can reproduce correct axial
anomaly for sufficiently smooth gauge configurations, provided that it is
exponentially-local, doublers-free, and has correct continuum behavior. In this
paper, we calculate the axial anomaly of this lattice Dirac operator in weak
coupling perturbation theory, and show that it recovers the topological charge
density in the continuum limit.Comment: 25 pages, v2: calculation up to O(g^4) for nonabelian gauge
backgroun
Security Allocation in Networked Control Systems under Stealthy Attacks
This paper considers the problem of security allocation in a networked
control system under stealthy attacks in which the system is comprised of
interconnected subsystems represented by vertices. A malicious adversary
selects a single vertex on which to conduct a stealthy data injection attack to
maximally disrupt the local performance while remaining undetected. On the
other hand, a defender selects several vertices on which to allocate defense
resources against the adversary. First, the objectives of the adversary and the
defender with uncertain targets are formulated in probabilistic ways, resulting
in an expected worst-case impact of stealthy attacks. Next, we provide a
graph-theoretic necessary and sufficient condition under which the cost for the
defender and the expected worst-case impact of stealthy attacks are bounded.
This condition enables the defender to restrict the admissible actions to a
subset of available vertex sets. Then, we cast the problem of security
allocation in a Stackelberg game-theoretic framework. Finally, the contribution
of this paper is highlighted by utilizing the proposed admissible actions of
the defender in the context of large-scale networks. A numerical example of a
50-vertex networked control system is presented to validate the obtained
results.Comment: 11 pages, 3 figures, and 1 table, journal submissio
Infrared spectroscopy of Landau levels in graphene
We report infrared studies of the Landau level (LL) transitions in single
layer graphene. Our specimens are density tunable and show \textit{in situ}
half-integer quantum Hall plateaus. Infrared transmission is measured in
magnetic fields up to B=18 T at selected LL fillings. Resonances between hole
LLs and electron LLs, as well as resonances between hole and electron LLs are
resolved. Their transition energies are proportional to and the
deduced band velocity is m/s. The lack of
precise scaling between different LL transitions indicates considerable
contributions of many-particle effects to the infrared transition energies.Comment: 4 pages, 3 figures, to appear in Phys. Rev. Let
A Zero-Sum Game Framework for Optimal Sensor Placement in Uncertain Networked Control Systems under Cyber-Attacks
This paper proposes a game-theoretic approach to address the problem of
optimal sensor placement against an adversary in uncertain networked control
systems. The problem is formulated as a zero-sum game with two players, namely
a malicious adversary and a detector. Given a protected performance vertex, we
consider a detector, with uncertain system knowledge, that selects another
vertex on which to place a sensor and monitors its output with the aim of
detecting the presence of the adversary. On the other hand, the adversary, also
with uncertain system knowledge, chooses a single vertex and conducts a
cyber-attack on its input. The purpose of the adversary is to drive the attack
vertex as to maximally disrupt the protected performance vertex while remaining
undetected by the detector. As our first contribution, the game payoff of the
above-defined zero-sum game is formulated in terms of the Value-at-Risk of the
adversary's impact. However, this game payoff corresponds to an intractable
optimization problem. To tackle the problem, we adopt the scenario approach to
approximately compute the game payoff. Then, the optimal monitor selection is
determined by analyzing the equilibrium of the zero-sum game. The proposed
approach is illustrated via a numerical example of a 10-vertex networked
control system.Comment: 8 pages, 3 figues, Accepted to the 61st Conference on Decision and
Control, Cancun, December 202
Electron surface layer at the interface of a plasma and a dielectric wall
We study the potential and the charge distribution across the interface of a
plasma and a dielectric wall. For this purpose, the charge bound to the wall is
modelled as a quasi-stationary electron surface layer which satisfies Poisson's
equation and minimizes the grand canonical potential of the wall-thermalized
excess electrons constituting the wall charge. Based on an effective model for
a graded interface taking into account the image potential and the offset of
the conduction band to the potential just outside the dielectric, we
specifically calculate the potential and the electron distribution for
magnesium oxide, silicon dioxide and sapphire surfaces in contact with a helium
discharge. Depending on the electron affinity of the surface, we find two
vastly different behaviors. For negative electron affinity, electrons do not
penetrate into the wall and an external surface charge is formed in the image
potential, while for positive electron affinity, electrons penetrate into the
wall and a space charge layer develops in the interior of the dielectric. We
also investigate how the electron surface layer merges with the bulk of the
dielectric.Comment: 15 pages, 9 figures, accepted versio
Evaluating quasilocal energy and solving optimal embedding equation at null infinity
We study the limit of quasilocal energy defined in [7] and [8] for a family
of spacelike 2-surfaces approaching null infinity of an asymptotically flat
spacetime. It is shown that Lorentzian symmetry is recovered and an
energy-momentum 4-vector is obtained. In particular, the result is consistent
with the Bondi-Sachs energy-momentum at a retarded time. The quasilocal mass in
[7] and [8] is defined by minimizing quasilocal energy among admissible
isometric embeddings and observers. The solvability of the Euler-Lagrange
equation for this variational problem is also discussed in both the
asymptotically flat and asymptotically null cases. Assuming analyticity, the
equation can be solved and the solution is locally minimizing in all orders. In
particular, this produces an optimal reference hypersurface in the Minkowski
space for the spatial or null exterior region of an asymptotically flat
spacetime.Comment: 22 page
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