717 research outputs found
Entanglement and criticality in translational invariant harmonic lattice systems with finite-range interactions
We discuss the relation between entanglement and criticality in
translationally invariant harmonic lattice systems with non-randon,
finite-range interactions. We show that the criticality of the system as well
as validity or break-down of the entanglement area law are solely determined by
the analytic properties of the spectral function of the oscillator system,
which can easily be computed. In particular for finite-range couplings we find
a one-to-one correspondence between an area-law scaling of the bi-partite
entanglement and a finite correlation length. This relation is strict in the
one-dimensional case and there is strog evidence for the multi-dimensional
case. We also discuss generalizations to couplings with infinite range.
Finally, to illustrate our results, a specific 1D example with nearest and
next-nearest neighbor coupling is analyzed.Comment: 4 pages, one figure, revised versio
Diffusion on non exactly decimable tree-like fractals
We calculate the spectral dimension of a wide class of tree-like fractals by
solving the random walk problem through a new analytical technique, based on
invariance under generalized cutting-decimation transformations. These fractals
are generalizations of the NTD lattices and they are characterized by non
integer spectral dimension equal or greater then 2, non anomalous diffusion
laws, dynamical dimension splitting and absence of phase transitions for spin
models.Comment: 5 pages Latex, 3 figures (figures are poscript files
Percolation model for nodal domains of chaotic wave functions
Nodal domains are regions where a function has definite sign. In recent paper
[nlin.CD/0109029] it is conjectured that the distribution of nodal domains for
quantum eigenfunctions of chaotic systems is universal. We propose a
percolation-like model for description of these nodal domains which permits to
calculate all interesting quantities analytically, agrees well with numerical
simulations, and due to the relation to percolation theory opens the way of
deeper understanding of the structure of chaotic wave functions.Comment: 4 pages, 6 figures, Late
Numerical indications of a q-generalised central limit theorem
We provide numerical indications of the -generalised central limit theorem
that has been conjectured (Tsallis 2004) in nonextensive statistical mechanics.
We focus on binary random variables correlated in a {\it scale-invariant}
way. The correlations are introduced by imposing the Leibnitz rule on a
probability set based on the so-called -product with . We show
that, in the large limit (and after appropriate centering, rescaling, and
symmetrisation), the emerging distributions are -Gaussians, i.e., , with , and
with coefficients approaching finite values . The
particular case recovers the celebrated de Moivre-Laplace theorem.Comment: Minor improvements and corrections have been introduced in the new
version. 7 pages including 4 figure
The Counterpart Principle of Analogical Support by Structural Similarity
We propose and investigate an Analogy Principle in the context of Unary Inductive Logic based on a notion of support by structural similarity which is often employed to motivate scientific conjectures
Uniqueness of the solution to inverse scattering problem with scattering data at a fixed direction of the incident wave
Let be real-valued compactly supported sufficiently smooth function.
It is proved that the scattering data , determine uniquely. Here is a fixed
direction of the incident plane wave
An insurance value modeling approach that captures the wider value of a novel antimicrobial to health systems, patients, and the population.
Background: Traditional health economic evaluations of antimicrobials currently underestimate their value to wider society. They can be supplemented by additional value elements including insurance value, which captures the value of an antimicrobial in preventing or mitigating impacts of adverse risk events. Despite being commonplace in other sectors, constituents of the impacts and approaches for estimating insurance value have not been investigated. Objectives: This study assessed the insurance value of a novel gram-negative antimicrobial from operational healthcare, wider population health, productivity, and informal care perspectives. Methods: A novel mixed-methods approach was used to model insurance value in the United Kingdom: (1) literature review and multidisciplinary expert workshops to identify risk events for 4 relevant scenarios: ward closures, unavoidable shortage of conventional antimicrobials, viral respiratory pandemics, and catastrophic antimicrobial resistance (AMR); (2) parameterizing mitigable costs and frequencies of risk events across perspectives and scenarios; (3) estimating insurance value through a Monte Carlo simulation model for extreme events and a dynamic disease transmission model. Results: The mean insurance value across all scenarios and perspectives over 10 years in the UK was £718 million, should AMR remain unchanged, where only £134 million related to operational healthcare costs. It would be 50%-70% higher if AMR steadily increased or if a more risk-averse view (1-in-10 year downside) of future events is taken. Discussion: The overall insurance value if AMR remains at current levels (a conservative projection), is over 5 times greater than insurance value from just the operational healthcare costs perspective, traditionally the sole perspective used in health budgeting. Insurance value was generally larger for nationwide or universal (catastrophic AMR, pandemic, and conventional antimicrobial shortages) rather than localized (ward closure) scenarios, across perspectives. Components of this insurance value match previously published estimates of operational costs and mortality impacts. Conclusions: Insurance value of novel antimicrobials can be systematically modeled and substantially augments their traditional health economic value in normal circumstances. These approaches are generalizable to similar health interventions and form a framework for health systems and governments to capture broader value in health technology assessments, improve healthcare access, and increase resilience by planning for adverse scenarios
Phase transitions with four-spin interactions
Using an extended Lee-Yang theorem and GKS correlation inequalities, we
prove, for a class of ferromagnetic multi-spin interactions, that they will
have a phase transition(and spontaneous magnetization) if, and only if, the
external field (and the temperature is low enough). We also show the
absence of phase transitions for some nonferromagnetic interactions. The FKG
inequalities are shown to hold for a larger class of multi-spin interactions
Random walks on graphs: ideas, techniques and results
Random walks on graphs are widely used in all sciences to describe a great
variety of phenomena where dynamical random processes are affected by topology.
In recent years, relevant mathematical results have been obtained in this
field, and new ideas have been introduced, which can be fruitfully extended to
different areas and disciplines. Here we aim at giving a brief but
comprehensive perspective of these progresses, with a particular emphasis on
physical aspects.Comment: LateX file, 34 pages, 13 jpeg figures, Topical Revie
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