60,702 research outputs found
Adaptive just-in-time code diversification
We present a method to regenerate diversified code dynamically in a Java bytecode JIT compiler, and to update the diversification frequently during the execution of the program. This way, we can significantly reduce the time frame in which attackers can let a program leak useful address space information and subsequently use the leaked information in memory exploits. A proof of concept implementation is evaluated, showing that even though code is recompiled frequently, we can achieved smaller overheads than the previous state of the art, which generated diversity only once during the whole execution of a program
Conductance spectra of metallic nanotube bundles
We report a first principles analysis of electronic transport characteristics
for (n,n) carbon nanotube bundles. When n is not a multiple of 3, inter-tube
coupling causes universal conductance suppression near Fermi level regardless
of the rotational arrangement of individual tubes. However, when n is a
multiple of 3, the bundles exhibit a diversified conductance dependence on the
orientation details of the constituent tubes. The total energy of the bundle is
also sensitive to the orientation arrangement only when n is a multiple of 3.
All the transport properties and band structures can be well understood from
the symmetry consideration of whether the rotational symmetry of the individual
tubes is commensurate with that of the bundle
Closed formula for the relative entropy of entanglement
The long-standing problem of finding a closed formula for the relative
entropy of entanglement (REE) for two qubits is addressed. A compact-form
solution to the inverse problem, which characterizes an entangled state for a
given closest separable state, is obtained. Analysis of the formula for a large
class of entangled states strongly suggests that a compact analytical solution
of the original problem, which corresponds to finding the closest separable
state for a given entangled state, can be given only in some special cases. A
few applications of the compact-form formula are given to show additivity of
the REE, to relate the REE with the Rains upper bound for distillable
entanglement, and to show that a Bell state does not have a unique closest
separable state.Comment: 7 pages, the title was modified as suggested by the PRA editor
Relative entropy of entanglement for certain multipartite mixed states
We prove conjectures on the relative entropy of entanglement (REE) for two
families of multipartite qubit states. Thus, analytic expressions of REE for
these families of states can be given. The first family of states are composed
of mixture of some permutation-invariant multi-qubit states. The results
generalized to multi-qudit states are also shown to hold. The second family of
states contain D\"ur's bound entangled states. Along the way, we have discussed
the relation of REE to two other measures: robustness of entanglement and
geometric measure of entanglement, slightly extending previous results.Comment: Single column, 22 pages, 9 figures, comments welcom
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Squeeze-film levitation characteristics of plates excited by piezoelectric actuators
A small mass is levitated by a vibrating plate with an arrangement of four piezoelectric actuators that generate a squeeze-film in the gap between the plate and the mass. Different arrangements of actuators and plate design are explored using simulation in order to produce better performance
Critical Dynamical Exponent of the Two-Dimensional Scalar Model with Local Moves
We study the scalar one-component two-dimensional (2D) model by
computer simulations, with local Metropolis moves. The equilibrium exponents of
this model are well-established, e.g. for the 2D model
and . The model has also been conjectured to belong to the Ising
universality class. However, the value of the critical dynamical exponent
is not settled. In this paper, we obtain for the 2D model using
two independent methods: (a) by calculating the relative terminal exponential
decay time for the correlation function ,
and thereafter fitting the data as , where is the system
size, and (b) by measuring the anomalous diffusion exponent for the order
parameter, viz., the mean-square displacement (MSD) as , and from the numerically
obtained value , we calculate . For different values of the
coupling constant , we report that and
for the two methods respectively. Our results indicate that
is independent of , and is likely identical to that for the 2D
Ising model. Additionally, we demonstrate that the Generalised Langevin
Equation (GLE) formulation with a memory kernel, identical to those applicable
for the Ising model and polymeric systems, consistently capture the observed
anomalous diffusion behavior.Comment: 14 pages, 4 figures, 6 figure files, to appear in Phys. Rev.
Coexistence of Spin Density Wave and Triplet Superconductivity
We discuss the possibility of coexistence of spin density wave
(antiferromagnetism) and triplet superconductivity as a particular example of a
broad class of systems where the interplay of magnetism and superconductivity
is important. We focus on the case of quasi-one-dimensional metals, where it is
known experimentally that antiferromagnetism is in close proximity to triplet
superconductivity in the temperature versus pressure phase diagram. Over a
narrow range of pressures, we propose an intermediate non-uniform phase
consisting of alternating antiferromagnetic and triplet superconducting
stripes. Within the non-uniform phase there are also changes between two and
three dimensional behavior.Comment: Revtex4, 4 pages, 5 figure
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