3,089 research outputs found
An orientable time of flight detector for cosmic rays
Cosmic ray studies, in particular UHECR, can be in general supported by a
directional, easy deployable, simple and robust detector. The design of this
detector is based on the time of flight between two parallel tiles of
scintillator, to distinguish particle passing through in opposite directions;
by fine time resolution and pretty adjustable acceptance it is possible to
select upward(left)/downward(right) cosmic rays. It has been developed for an
array of detectors to measure upward from Earth-Skimming neutrino events
with energy above . The properties and performances of the detector
are discussed. Test results from a high noise environment are presented.Comment: 4 pages, Nuclear Instruments and methods, Proceedings Ricap0
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The effects of interbank networks on efficiency and stability in a macroeconomic agent-based model
We develop a macroeconomic agent-based model that consists of firms, banks, unions and households who interact on labour, goods, credit and interbank markets. The model endogenises pricing decisions by firms, wage setting by unions and interest rate setting by banks on both firm and interbank lending. Banks also set leverage targets and precautionary liquidity buffers on the basis of internal risk models. Our model produces endogenous fluctuations driven by the pricing behaviour of firms and the wage setting behaviour of unions. Fluctuations lead to loan defaults which are exacerbated as lenders reduce lending and charge higher interest rates, inducing a credit crunch. We also study how making the inter-banking network more connected affects the key outcomes of the economy and find that while the flow of funds from surplus banks to firms can be increased, the latter effect is soon dominated by increasing instability in the real sector as firms default at higher rates. While the banking sector experiences fewer defaults as a whole, losses on the interbank market increase as a source of bank defaults
Test results of a prototype designed to detect horizontal cosmic ray flux
In this paper we report test results from a prototype designed to detect
muons from horizontal air shower at large zenith angle,
. To detect horizontal tracks and their directions we
select them according the muon vertical equivalent charge and we measure the
time of flight with a time resolution of 800 ps. Several measurements are
collected at different zenith angles. The background studies performed with two
modules show that the main source is due to tracks crossing the module at the
same time. The upper limit of background flux for a single twin module is
estimated to be . We estimated the
size of the surface array necessary to detect the shower flux of the order of
if originated by Tau Air-Showers
secondaries of GZK neutrino Tau below the horizons.Comment: 12 pages, 13 figure
Electron muon identification by atmospheric shower and electron beam in a new concept of an EAS detector
We present results demonstrating the time resolution and /e separation
capabilities with a new concept of an EAS detector capable for measurements of
cosmic rays arriving with large zenith angles. This kind of detector has been
designed to be a part of a large area (several square kilometers) surface array
designed to measure Ultra High Energy (10-200 PeV) neutrinos using the
Earth-skimming technique. A criteria to identify electron-gammas is also shown
and the particle identification capability is tested by measurements in
coincidence with the KASKADE-GRANDE experiment in Karlsruhe, Germany.Comment: accepted by Astrophysical Journal on January 12 2015, 16 pages 3
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Centralized vs Decentralized Markets in the Laboratory: The Role of Connectivity
This paper compares the performance of centralized and decentralized markets experimentally. We constrain trading exchanges to happen on an exogenously predetermined network, representing the trading relationships in markets with differing levels of connectivity. Our experimental results show that, despite having lower trading volumes, decentralized markets are generally not less efficient. Although information can propagate quicker through highly connected markets, we show that higher connectivity also induces informed traders to trade faster and exploit further their information advantages before the information becomes fully incorporated into prices. This not only reduces market efficiency, but it increases wealth inequality. We show that, in more connected markets, informed traders trade not only relatively quicker, but also more, in the right direction, despite not doing it at better prices
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A multi-agent methodology to assess the effectiveness of alternative systemic risk adjusted capital requirements
We propose a multi-agent approach to compare the effectiveness of macro-prudential capital requirements, where banks are embedded in an artificial macroeconomy. Capital requirements are derived from systemic- risk metrics that reflect both the vulnerability or impact of financial in- stitutions. Our objective is to explore how systemic-risk measures could be translated in capital requirements and test them in a comprehensive framework. Based on our counterfactual scenarios, we find that macro- prudential capital requirements can mitigate systemic risk, but there is a trade-off between market- and balance-sheet-based policies in terms of banks’ losses and credit supply
Simulated Tempering: A New Monte Carlo Scheme
We propose a new global optimization method ({\em Simulated Tempering}) for
simulating effectively a system with a rough free energy landscape (i.e. many
coexisting states) at finite non-zero temperature. This method is related to
simulated annealing, but here the temperature becomes a dynamic variable, and
the system is always kept at equilibrium. We analyze the method on the Random
Field Ising Model, and we find a dramatic improvement over conventional
Metropolis and cluster methods. We analyze and discuss the conditions under
which the method has optimal performances.Comment: 12 pages, very simple LaTeX file, figures are not included, sorr
Mathematical formulations for scheduling jobs on identical parallel machines with family setup times and total weighted completion time minimization
This paper addresses the parallel machine scheduling problem with family dependent setup times and total weighted completion time minimization. In this problem, when two jobs j and k are scheduled consecutively on the same machine, a setup time is performed between the finishing time of j and the starting time of k if and only if j and k belong to different families. The problem is strongly NP-hard and is commonly addressed in the literature by heuristic approaches and by branch-and-bound algorithms. Achieving proven optimal solution is a challenging task even for small size instances. Our contribution is to introduce five novel mixed integer linear programs based on concepts derived from one-commodity, arc-flow and set covering formulations. Numerical experiments on more than 13000 benchmark instances show that one of the arc-flow models and the set covering model are quite efficient, as they provide on average better solutions than state-of-the-art approaches, with shorter computation times, and solve to proven optimality a large number of open instances from the literature
Off-Equilibrium Dynamics of a 4D Spin Glass with Asymmetric Couplings
We study the off-equilibrium dynamics of the Edwards-Anderson spin glass in
four dimensions under the influence of a non-hamiltonian perturbation. We find
that for small asymmetry the model behaves as the hamiltonian one, while for
large asymmetry the behaviour of the model can be well described by an
interrupted aging scenario. The autocorrelation function C(t_w+\tau,t_w) scales
as \tau/t_w^\beta, with \beta a function of the asymmetry. For very long
waiting times the previous regime crosses over to a time translational
invariant regime (TTI) with stretched exponential relaxation. The model does
not show signs of reaching a TTI regime for weak asymmetry, but in the aging
regime the exponent \beta is always different from one, showing a non trivial
aging scenario.Comment: Latex, 12 pages, 9 figure
A quantitative model of trading and price formation in financial markets
We use standard physics techniques to model trading and price formation in a
market under the assumption that order arrival and cancellations are Poisson
random processes. This model makes testable predictions for the most basic
properties of a market, such as the diffusion rate of prices, which is the
standard measure of financial risk, and the spread and price impact functions,
which are the main determinants of transaction cost. Guided by dimensional
analysis, simulation, and mean field theory, we find scaling relations in terms
of order flow rates. We show that even under completely random order flow the
need to store supply and demand to facilitate trading induces anomalous
diffusion and temporal structure in prices.Comment: 5 pages, 4 figure
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