12,100 research outputs found
Pure Nash Equilibria: Hard and Easy Games
We investigate complexity issues related to pure Nash equilibria of strategic
games. We show that, even in very restrictive settings, determining whether a
game has a pure Nash Equilibrium is NP-hard, while deciding whether a game has
a strong Nash equilibrium is SigmaP2-complete. We then study practically
relevant restrictions that lower the complexity. In particular, we are
interested in quantitative and qualitative restrictions of the way each players
payoff depends on moves of other players. We say that a game has small
neighborhood if the utility function for each player depends only on (the
actions of) a logarithmically small number of other players. The dependency
structure of a game G can be expressed by a graph DG(G) or by a hypergraph
H(G). By relating Nash equilibrium problems to constraint satisfaction problems
(CSPs), we show that if G has small neighborhood and if H(G) has bounded
hypertree width (or if DG(G) has bounded treewidth), then finding pure Nash and
Pareto equilibria is feasible in polynomial time. If the game is graphical,
then these problems are LOGCFL-complete and thus in the class NC2 of highly
parallelizable problems
Impact of temperature dependence of the energy loss on jet quenching observables
The quenching of jets (particles with ) in
ultra-relativistic heavy-ion collisions has been one of the main prediction and
discovery at RHIC. We have studied, by a simple jet quenching modeling, the
correlation between different observables like the nuclear modification factor
\Rapt, the elliptic flow and the ratio of quark to gluon suppression
. We show that the relation among these
observables is strongly affected by the temperature dependence of the energy
loss. In particular the large and and the nearly equal \Rapt of quarks
and gluons can be accounted for only if the energy loss occurs mainly around
the temperature and the flavour conversion is significant.Finally we
point out that the efficency in the conversion of the space eccentricity into
the momentum one () results to be quite smaller respect to the one coming
from elastic scatterings in a fluid with a viscosity to entropy density ratio
.Comment: 7 pages, 8 figures, Workshop WISH 201
Asymptotic robustness of Kelly's GLRT and Adaptive Matched Filter detector under model misspecification
A fundamental assumption underling any Hypothesis Testing (HT) problem is
that the available data follow the parametric model assumed to derive the test
statistic. Nevertheless, a perfect match between the true and the assumed data
models cannot be achieved in many practical applications. In all these cases,
it is advisable to use a robust decision test, i.e. a test whose statistic
preserves (at least asymptotically) the same probability density function (pdf)
for a suitable set of possible input data models under the null hypothesis.
Building upon the seminal work of Kent (1982), in this paper we investigate the
impact of the model mismatch in a recurring HT problem in radar signal
processing applications: testing the mean of a set of Complex Elliptically
Symmetric (CES) distributed random vectors under a possible misspecified,
Gaussian data model. In particular, by using this general misspecified
framework, a new look to two popular detectors, the Kelly's Generalized
Likelihood Ration Test (GLRT) and the Adaptive Matched Filter (AMF), is
provided and their robustness properties investigated.Comment: ISI World Statistics Congress 2017 (ISI2017), Marrakech, Morocco,
16-21 July 201
A novel stepwise micro-TESE approach in non obstructive azoospermia
Background: The purpose of the study was to investigate whether micro-TESE can improve sperm retrieval rate
(SRR) compared to conventional single TESE biopsy on the same testicle or to contralateral multiple TESE, by
employing a novel stepwise micro-TESE approach in a population of poor prognosis patients with non-obstructive
azoospermia (NOA).
Methods: Sixty-four poor prognosis NOA men undergoing surgical testicular sperm retrieval for ICSI, from March
2007 to April 2013, were included in this study. Patients inclusion criteria were a) previous unsuccessful TESE, b)
unfavorable histology (SCOS, MA, sclerahyalinosis), c) Klinefelter syndrome. We employed a stepwise micro-TESE
consisting three-steps: 1) single conventional TESE biopsy; 2) micro-TESE on the same testis; 3) contralateral multiple
TESE.
Results: SRR was 28.1 % (18/64). Sperm was obtained in both the initial single conventional TESE and in the
following micro-TESE. The positive or negative sperm retrieval was further confirmed by a contralateral multiple
TESE, when performed. No significant pre-operative predictors of sperm retrieval, including patients’ age, previous
negative TESE or serological markers (LH, FSH, inhibin B), were observed at univariate or multivariate analysis.
Micro-TESE (step 2) did not improve sperm retrieval as compared to single TESE biopsy on the same testicle
(step 1) or multiple contralateral TESE (step 3).
Conclusions: Stepwise micro-TESE could represent an optimal approach for sperm retrieval in NOA men. In
our view, it should be offered to NOA patients in order to gradually increase surgical invasiveness, when
necessary. Stepwise micro-TESE might also reduce the costs, time and efforts involved in surgery
Elliptic Flow from Non-equilibrium Initial Condition with a Saturation Scale
A current goal of relativistic heavy ion collisions experiments is the search
for a Color Glass Condensate as the limiting state of QCD matter at very high
density. In viscous hydrodynamics simulations, a standard Glauber initial
condition leads to estimate , while a Color Glass
Condensate modeling leads to at least a factor of 2 larger . Within a
kinetic theory approach based on a relativistic Boltzmann-like transport
simulation, we point out that the out-of-equilibrium initial distribution
proper of a Color Glass Condensate reduces the efficiency in building-up the
elliptic flow. Our main result at RHIC energy is that the available data on
are in agreement with a also for Color Glass
Condensate initial conditions, opening the possibility to describe
self-consistently also higher order flow, otherwise significantly
underestimated, and to pursue further the search for signatures of the Color
Glass Condensate.Comment: 6 pages, 4 figures. // Title changed, some discussion added, main
conclusions unchanged. Version accepted for publication on Phys. Lett.
Introduction to the Special Issue on Liminal Hotspots
This article introduces a special issue of Theory and Psychology on liminal hotspots. A liminal hotspot is an occasion during which people feel they are caught suspended in the circumstances of a transition that has become permanent. The liminal experiences of ambiguity and uncertainty that are typically at play in transitional circumstances acquire an enduring quality that can be described as a “hotspot”. Liminal hotspots are characterized by dynamics of paradox, paralysis, and polarization, but they also intensify the potential for pattern shift. The origins of the concept are described followed by an overview of the contributions to this special issue
Removal of carbon monoxide. Physical adsorption on natural and synthetic zeolites
The utilization of natural zeolite materials in the elimination of polluting gases is investigated. Carbon monoxide pollution is emphasized because its concentration may reach dangerous levels in places such as vehicle tunnels, underground parking lots, etc. The elimination of carbon monoxide is also of interest in some industrial processes relating to the production of pure gases
- …