11,031 research outputs found
CSCP: A new Get Away Special (GAS) project
The Get Away Special (GAS) program has instituted a new project called Complex Self Contained Payloads (CSCP) designed to support GAS type payloads that are beyond the scope of the GAS program. These payloads may be supported by GAS personnel and hardware and will fly as primary or secondary shuttle payloads. The definition, requirements and basic support package for CSCP's are discussed
Properties of nonfreeness: an entropy measure of electron correlation
"Nonfreeness" is the (negative of the) difference between the von Neumann
entropies of a given many-fermion state and the free state that has the same
1-particle statistics. It also equals the relative entropy of the two states in
question, i.e., it is the entropy of the given state relative to the
corresponding free state. The nonfreeness of a pure state is the same as its
"particle-hole symmetric correlation entropy", a variant of an established
measure of electron correlation. But nonfreeness is also defined for mixed
states, and this allows one to compare the nonfreeness of subsystems to the
nonfreeness of the whole. Nonfreeness of a part does not exceed that in the
whole; nonfreeness is additive over independent subsystems; and nonfreeness is
superadditive over subsystems that are independent on the 1-particle level.Comment: 20 pages. Submitted to Phys. Rev.
Optimal Explicit Strong Stability Preserving Runge--Kutta Methods with High Linear Order and optimal Nonlinear Order
High order spatial discretizations with monotonicity properties are often
desirable for the solution of hyperbolic PDEs. These methods can advantageously
be coupled with high order strong stability preserving time discretizations.
The search for high order strong stability time-stepping methods with large
allowable strong stability coefficient has been an active area of research over
the last two decades. This research has shown that explicit SSP Runge--Kutta
methods exist only up to fourth order. However, if we restrict ourselves to
solving only linear autonomous problems, the order conditions simplify and this
order barrier is lifted: explicit SSP Runge--Kutta methods of any linear order
exist. These methods reduce to second order when applied to nonlinear problems.
In the current work we aim to find explicit SSP Runge--Kutta methods with large
allowable time-step, that feature high linear order and simultaneously have the
optimal fourth order nonlinear order. These methods have strong stability
coefficients that approach those of the linear methods as the number of stages
and the linear order is increased. This work shows that when a high linear
order method is desired, it may be still be worthwhile to use methods with
higher nonlinear order
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