163 research outputs found
Optimization Strategies in Complex Systems
We consider a class of combinatorial optimization problems that emerge in a
variety of domains among which: condensed matter physics, theory of financial
risks, error correcting codes in information transmissions, molecular and
protein conformation, image restoration. We show the performances of two
algorithms, the``greedy'' (quick decrease along the gradient) and
the``reluctant'' (slow decrease close to the level curves) as well as those of
a``stochastic convex interpolation''of the two. Concepts like the average
relaxation time and the wideness of the attraction basin are analyzed and their
system size dependence illustrated.Comment: 8 pages, 3 figure
On a Statistical Mechanics Approach to Some Problems of the Social Sciences
This work is a survey of some results on a statistical mechanics approach to the social sciences emerged in the last two decades. The pioneering work of Daniel McFadden, known as discrete choice theory, is interpreted in terms of a non-interacting model and extended along the lines of the Brock and Durlauf interacting systems. The generalization to the multi-populated model is presented and two specific case studies are reviewed with their phenomenological and theoretical analysis
On a Statistical Mechanics Approach to Some Problems of the Social Sciences
This work is a survey of some results on a statistical mechanics approach to the social sciences emerged in the last two decades. The pioneering work of Daniel McFadden, known as discrete choice theory, is interpreted in terms of a non-interacting model and extended along the lines of the Brock and Durlauf interacting systems. The generalization to the multi-populated model is presented and two specific case studies are reviewed with their phenomenological and theoretical analysis
O(N) Fluctuations and Lattice Distortions in 1-Dimensional Systems
Statistical mechanics harmonizes mechanical and thermodynamical quantities, via the notion of local thermodynamic equilibrium (LTE). In absence of external drivings, LTE becomes equilibrium tout court, and states are characterized by several thermodynamic quantities, each of which is associated with negligibly fluctuating microscopic properties. Under small driving and LTE, locally conserved quantities are transported as prescribed by linear hydrodynamic laws, in which the local material properties of the system are represented by the transport coefficients. In 1-dimensional systems, on the other hand, various anomalies are reported, such as the dependence of the heat conductivity on the global state, rather than on the local state. Such deductions, that rely on the existence of thermodynamic quantities like temperature and heat, are here interpreted within the framework of boundary driven 1-dimensional Lennard-Jones chains of N oscillators. It is found that these chains experience non-negligible O(N) lattice distortions, resulting in strongly inhomogeneous systems, and O(N) position fluctuations, that are in contrast with the requirements of LTE
On the structure of correlations in the three dimensional spin glasses
We investigate the low temperature phase of three-dimensional
Edwards-Anderson model with Bernoulli random couplings. We show that at a fixed
value of the overlap the model fulfills the clustering property: the
connected correlation functions between two local overlaps decay as a power
whose exponent is independent of for all . Our findings
are in agreement with the RSB theory and show that the overlap is a good order
parameter.Comment: 5 pages, 5 figure
Combined Effects of Age and Comorbidities on Electrocardiographic Parameters in a Large Non-Selected Population
Background: Previous studies have evaluated average electrocardiographic (ECG) values in healthy subjects or specific subpopulations. However, none have evaluated ECG average values in not selected populations, so we examined ECG changes with respect to age and sex in a large primary population. Methods: From digitized ECG stored from 2008 to 2021 in the Modena province, 130,471 patients were enrolled. Heart rate, P, QRS and T wave axis, P, QRS and T wave duration, PR interval, QTc, and frontal QRS-T angle were evaluated. Results: All ECG parameters showed a dependence on age, but only some of them with a straight-line correlation: QRS axis (p < 0.001, R2 = 0.991, r = 0.996), PR interval (p < 0.001, R2 = 0.978, r = 0.989), QTc (p < 0.001, R2 = 0.935, r = 0.967), and, in over 51.5 years old, QRS-T angle (p < 0.001, R2 = 0.979, r = 0.956). Differences between females and males and in different clinical settings were observed. Conclusions: ECG changes with ageing are explainable by intrinsic modifications of the heart and thorax and with the appearance of cardiovascular diseases and comorbidities. Age-related reference values were computed and applicable in clinical practice. Significant deviations from mean values and from Z-scores should be investigated
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