102 research outputs found
Fluctuations and response in a non-equilibrium micron-sized system
The linear response of non-equilibrium systems with Markovian dynamics
satisfies a generalized fluctuation-dissipation relation derived from time
symmetry and antisymmetry properties of the fluctuations. The relation involves
the sum of two correlation functions of the observable of interest: one with
the entropy excess and the second with the excess of dynamical activity with
respect to the unperturbed process, without recourse to anything but the
dynamics of the system. We illustrate this approach in the experimental
determination of the linear response of the potential energy of a Brownian
particle in a toroidal optical trap. The overdamped particle motion is
effectively confined to a circle, undergoing a periodic potential and driven
out of equilibrium by a non-conservative force. Independent direct and indirect
measurements of the linear response around a non-equilibrium steady state are
performed in this simple experimental system. The same ideas are applicable to
the measurement of the response of more general non-equilibrium micron-sized
systems immersed in Newtonian fluids either in stationary or non-stationary
states and possibly including inertial degrees of freedom.Comment: 12 pages, submitted to J. Stat. Mech., revised versio
Stretched exponentials from superstatistics
Distributions exhibiting fat tails occur frequently in many different areas
of science. A dynamical reason for fat tails can be a so-called
superstatistics, where one has a superposition of local Gaussians whose
variance fluctuates on a rather large spatio-temporal scale. After briefly
reviewing this concept, we explore in more detail a class of superstatistics
that hasn't been subject of many investigations so far, namely superstatistics
for which a suitable power beta^eta of the local inverse temperature beta is
chi^2-distributed. We show that eta >0 leads to power law distributions, while
eta <0 leads to stretched exponentials. The special case eta=1 corresponds to
Tsallis statistics and the special case eta=-1 to exponential statistics of the
square root of energy. Possible applications for granular media and
hydrodynamic turbulence are discussed.Comment: 10 pages. Proceedings of NEXT-SigmaPhi conference, Kolymbari, 13-18
August 200
Nonequilibrium Linear Response for Markov Dynamics, II: Inertial Dynamics
We continue our study of the linear response of a nonequilibrium system. This
Part II concentrates on models of open and driven inertial dynamics but the
structure and the interpretation of the result remain unchanged: the response
can be expressed as a sum of two temporal correlations in the unperturbed
system, one entropic, the other frenetic. The decomposition arises from the
(anti)symmetry under time-reversal on the level of the nonequilibrium action.
The response formula involves a statistical averaging over explicitly known
observables but, in contrast with the equilibrium situation, they depend on the
model dynamics in terms of an excess in dynamical activity. As an example, the
Einstein relation between mobility and diffusion constant is modified by a
correlation term between the position and the momentum of the particle
Reliability of Logic-in-Memory Circuits in Resistive Memory Arrays
Producción CientíficaLogic-in-memory (LiM) circuits based on resistive random access memory (RRAM) devices and the material implication logic are promising candidates for the development of low-power computing devices that could fulfill the growing demand of distributed computing systems. However, these circuits are affected by many reliability challenges that arise from device nonidealities (e.g., variability) and the characteristics of the employed circuit architecture. Thus, an accurate investigation of the variability at the array level is needed to evaluate the reliability and performance of such circuit architectures. In this work, we explore the reliability and performance of smart IMPLY (SIMPLY) (i.e., a recently proposed LiM architecture with improved reliability and performance) on two 4-kb RRAM arrays based on different resistive switching oxides integrated in the back end of line (BEOL) of the 0.25-μm BiCMOS process. We analyze the tradeoff between reliability and energy consumption of SIMPLY architecture by exploiting the results of an extensive array-level variability characterization of the two technologies. Finally, we study the worst case performance of a full adder implemented with the SIMPLY architecture and benchmark it on the analogous CMOS implementation.European Union’s Horizon 2020 Research and Innovation Programme under Grant 64863
Is deliberation equitable? Evidence from transcripts of village meetings in south India
Abstract Deliberative decision-making processes are becoming increasingly important around the world to make important decisions about public and private goods allocation, but there is very little empirical evidence about how they actually work. In this paper we use data from India extracted from 131 transcripts of village meetings matched with data from household surveys conducted in the same villages prior to the meetings, to study whose preferences are re ‡ected in the meetings. The meetings are constitutionally empowered to make decisions about public and private goods. We …nd that the more land a person owns the higher the likelihood her preference is mentioned in the meeting, the longer the amount of time spend discussing this preference, and the higher the likelihood that a decision to provide or repair this public or private good is taken. At the same time, the voices of disadvantaged castes, while not dominating the meeting, are also heard. On the other hand, the preferences of Muslims are given less time. High village literacy and the presence of higher level o¢ cials during village meetings mitigate the power of the landed, but political reservations for low castes for the post of village president increase the power of the landed. We are grateful to Babu Dasari Srinivas and Jillian Waid for valuable research assistance, and to SRI-IMRB for conducting the …eldwork. Valuable suggestions were provide
Transnational Access to Research Facilities: an EPOS service to promote multi-domain Solid Earth Sciences in Europe
Transnational access (TNA) allows cross-border, short-term and frequently free-of-charge access to world-class research facilities, to foster collaborations and exchanges of experience. Specifically, TNA aims to encourage open science and innovation and to increase the efficient and effective use of scientific infrastructure. Within EPOS, the European Plate Observing System, the Volcano Observatories and Multi-scale Laboratories communities have offered TNA to their high-quality research facilities through national and European funding. This experience has allowed the definition, design, and testing of procedures and activities needed to provide transnational access inn the EPOS context. In this paper, the EPOS community describes the main objectives for the provision of transnational access in the EPOS framework, based on previous experiences. It includes practical procedures for managing transnational access from a legal, governance, and financial perspective, and proposes logistical and technical solutions to effectively execute transnational access activities. In addition, it provides an outlook on the inclusion of new thematic communities within the TNA framework, and addresses the challenges of providing market-driven access to industry.publishedVersio
ERIS: revitalising an adaptive optics instrument for the VLT
ERIS is an instrument that will both extend and enhance the fundamental
diffraction limited imaging and spectroscopy capability for the VLT. It will
replace two instruments that are now being maintained beyond their operational
lifetimes, combine their functionality on a single focus, provide a new
wavefront sensing module that makes use of the facility Adaptive Optics System,
and considerably improve their performance. The instrument will be competitive
with respect to JWST in several regimes, and has outstanding potential for
studies of the Galactic Center, exoplanets, and high redshift galaxies. ERIS
had its final design review in 2017, and is expected to be on sky in 2020. This
contribution describes the instrument concept, outlines its expected
performance, and highlights where it will most excel.Comment: 12 pages, Proc SPIE 10702 "Ground-Based and Airborne Instrumentation
for Astronomy VII
Making maps of cosmic microwave background polarization for B-mode studies: The POLARBEAR example
Analysis of cosmic microwave background (CMB) datasets typically requires some filtering of the raw time-ordered data. For instance, in the context of ground-based observations, filtering is frequently used to minimize the impact of low frequency noise, atmospheric contributions and/or scan synchronous signals on the resulting maps. In this work we have explicitly constructed a general filtering operator, which can unambiguously remove any set of unwanted modes in the data, and then amend the map-making procedure in order to incorporate and correct for it. We show that such an approach is mathematically equivalent to the solution of a problem in which the sky signal and unwanted modes are estimated simultaneously and the latter are marginalized over. We investigated the conditions under which this amended map-making procedure can render an unbiased estimate of the sky signal in realistic circumstances. We then discuss the potential implications of these observations on the choice of map-making and power spectrum estimation approaches in the context of B-mode polarization studies. Specifically, we have studied the effects of time-domain filtering on the noise correlation structure in the map domain, as well as impact it may haveon the performance of the popular pseudo-spectrum estimators. We conclude that although maps produced by the proposed estimators arguably provide the most faithful representation of the sky possible given the data, they may not straightforwardly lead to the best constraints on the power spectra of the underlying sky signal and special care may need to be taken to ensure this is the case. By contrast, simplified map-makers which do not explicitly correct for time-domain filtering, but leave it to subsequent steps in the data analysis, may perform equally well and be easier and faster to implement. We focused on polarization-sensitive measurements targeting the B-mode component of the CMB signal and apply the proposed methods to realistic simulations based on characteristics of an actual CMB polarization experiment, POLARBEAR. Our analysis and conclusions are however more generally applicable. \ua9 ESO, 2017
MORFEO enters final design phase
MORFEO (Multi-conjugate adaptive Optics Relay For ELT Observations, formerly
MAORY), the MCAO system for the ELT, will provide diffraction-limited optical
quality to the large field camera MICADO. MORFEO has officially passed the
Preliminary Design Review and it is entering the final design phase. We present
the current status of the project, with a focus on the adaptive optics system
aspects and expected milestones during the next project phase
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