1,940 research outputs found
Energy correlations for a random matrix model of disordered bosons
Linearizing the Heisenberg equations of motion around the ground state of an
interacting quantum many-body system, one gets a time-evolution generator in
the positive cone of a real symplectic Lie algebra. The presence of disorder in
the physical system determines a probability measure with support on this cone.
The present paper analyzes a discrete family of such measures of exponential
type, and does so in an attempt to capture, by a simple random matrix model,
some generic statistical features of the characteristic frequencies of
disordered bosonic quasi-particle systems. The level correlation functions of
the said measures are shown to be those of a determinantal process, and the
kernel of the process is expressed as a sum of bi-orthogonal polynomials. While
the correlations in the bulk scaling limit are in accord with sine-kernel or
GUE universality, at the low-frequency end of the spectrum an unusual type of
scaling behavior is found.Comment: 20 pages, 3 figures, references adde
Correlation of creep rate with microstructural changes during high temperature creep
Creep tests were conducted on Haynes 188 cobalt-base alloy and alpha titanium. The tests on Haynes 188 were conducted at 1600 F and 1800 F for stresses from 3 to 20 ksi, and the as-received, mill-annealed results were compared to specimens given 5%, 10%, and 15% room temperature prestrains and then annealed one hour at 1800 F. The tests on alpha titanium were performed at 7,250 and 10,000 psi at 500 C. One creep test was done at 527 C and 10,000 psi to provide information on kinetics. Results for annealed titanium were compared to specimens given 10% and 20% room temperature prestrains followed by 100 hours recovery at 550 C. Electron microscopy was used to relate dislocation and precipitate structure to the creep behavior of the two materials. The results on Haynes 188 alloy reveal that the time to reach 0.5% creep strain at 1600 F increases with increasing prestrain for exposure times less than 1,000 hours, the increase at 15% prestrain being more than a factor of ten
Analysis of the infinity-replica symmetry breaking solution of the Sherrington-Kirkpatrick model
In this work we analyse the Parisi's infinity-replica symmetry breaking
solution of the Sherrington - Kirkpatrick model without external field using
high order perturbative expansions. The predictions are compared with those
obtained from the numerical solution of the infinity-replica symmetry breaking
equations which are solved using a new pseudo-spectral code which allows for
very accurate results. With this methods we are able to get more insight into
the analytical properties of the solutions. We are also able to determine
numerically the end-point x_{max} of the plateau of q(x) and find that lim_{T
--> 0} x_{max}(T) > 0.5.Comment: 15 pages, 11 figures, RevTeX 4.
Quenched Computation of the Complexity of the Sherrington-Kirkpatrick Model
The quenched computation of the complexity in the
Sherrington-Kirkpatrick model is presented. A modified Full Replica
Symmetry Breaking Ansatz is introduced in order to study the complexity
dependence on the free energy. Such an Ansatz corresponds to require
Becchi-Rouet-Stora-Tyutin supersymmetry. The complexity computed this way is
the Legendre transform of the free energy averaged over the quenched disorder.
The stability analysis shows that this complexity is inconsistent at any free
energy level but the equilibirum one. The further problem of building a
physically well defined solution not invariant under supersymmetry and
predicting an extensive number of metastable states is also discussed.Comment: 19 pages, 13 figures. Some formulas added corrected, changes in
discussion and conclusion, one figure adde
Synthesis of Knowledge: Fire History and Climate Change
This report synthesizes available fire history and climate change scientific knowledge to aid managers with fire decisions in the face of ongoing 21st century climate change. Fire history and climate change (FHCC) have been ongoing for over 400 million years of Earth history, but increasing human influences during the Holocene Epoch have changed both climate and fire regimes. We describe basic concepts of climate science and explain the causes of accelerating 21st century climate change. Fire regimes and ecosystem classifications serve to unify ecological and climate factors influencing fire, and are useful for applying fire history and climate change information to specific ecosystems. Variable and changing patterns of climate-fire interaction occur over different time and space scales that shape use of FHCC knowledge. Ecosystem differences in fire regimes, climate change, and available fire history mean that using an ecosystem-specific view will be beneficial when applying FHCC knowledge
Entanglement of random vectors
We analytically calculate the average value of i-th largest Schmidt
coefficient for random pure quantum states. Schmidt coefficients, i.e.,
eigenvalues of the reduced density matrix, are expressed in the limit of large
Hilbert space size and for arbitrary bipartite splitting as an implicit
function of index i.Comment: 8 page
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