32,877 research outputs found
When do correlations increase with firing rates in recurrent networks?
A central question in neuroscience is to understand how noisy firing patterns are used to transmit information. Because neural spiking is noisy, spiking patterns are often quantified via pairwise correlations, or the probability that two cells will spike coincidentally, above and beyond their baseline firing rate. One observation frequently made in experiments, is that correlations can increase systematically with firing rate. Theoretical studies have determined that stimulus-dependent correlations that increase with firing rate can have beneficial effects on information coding; however, we still have an incomplete understanding of what circuit mechanisms do, or do not, produce this correlation-firing rate relationship. Here, we studied the relationship between pairwise correlations and firing rates in recurrently coupled excitatory-inhibitory spiking networks with conductance-based synapses. We found that with stronger excitatory coupling, a positive relationship emerged between pairwise correlations and firing rates. To explain these findings, we used linear response theory to predict the full correlation matrix and to decompose correlations in terms of graph motifs. We then used this decomposition to explain why covariation of correlations with firing rate—a relationship previously explained in feedforward networks driven by correlated input—emerges in some recurrent networks but not in others. Furthermore, when correlations covary with firing rate, this relationship is reflected in low-rank structure in the correlation matrix
Comment on ``Dynamic behavior of anisotropic non-equilibrium driving lattice gases''
In a recent Letter Albano and Saracco study the dynamic critical behavior of
some anisotropic driven lattice gases by Monte Carlo (MC) simulations. In this
Comment we point out that the Ans\"atze they use to relate the measured scaling
exponents with the critical exponents analytically computed within different
field-theoretical approaches do not take properly into account the strongly
anisotropic nature of the phase transition, by implicitly assuming
. As a consequence, at variance with the claims
by the authors, their MC data are not conclusive to determine which one of the
field theories proposed in the literature correctly describes the universal
properties of the phase transition in these lattice gases.Comment: 1 pag
BG Group and “Conditions” to Arbitral Jurisdiction
Although the Supreme Court has over the last decade generated a robust body of arbitration caselaw, its first decision in the area of investment arbitration under a Bilateral Investment Treaty was only handed down in 2014. BG Group v. Argentina was widely anticipated and has attracted much notice, and general approval, on the part of the arbitration community. In this paper we assess the Court’s decision from two different perspectives—the first attempts to situate it in the discourse of the American law of commercial arbitration; the second considers it in light of the expectations of the international community surrounding the proper construction of Conventions between states.
Our initial goal had been to write jointly, with the hope that we could bridge our differences to find, if not common, at least neighboring, ground. On some points we did so, but ultimately our divergent appreciations of the proper way to interpret the condition precedent in the investment treaty in BG Group overcame the idealism with which we commenced the project. Nonetheless we have decided to present the two papers together to emphasize the dichotomous approaches to treaty interpretation that two moderately sensible people, who inhabit overlapping but non-congruent interpretive communities, can have.The Kay Bailey Hutchison Center for Energy, Law, and Busines
On the Evaluation of Compton Scattering Amplitudes in String Theory
We consider the Compton amplitude for the scattering of a photon and a
(massless) ``electron/positron'' at one loop (i.e. genus one) in a
four-dimensional fermionic heterotic string model. Starting from the
bosonization of the world-sheet fermions needed to explicitly construct the
spin-fields representing the space-time fermions, we present all the steps of
the computation which leads to the explicit form of the amplitude as an
integral of modular forms over the moduli space.Comment: 41 pages, Late
Internames: a name-to-name principle for the future Internet
We propose Internames, an architectural framework in which names are used to
identify all entities involved in communication: contents, users, devices,
logical as well as physical points involved in the communication, and services.
By not having a static binding between the name of a communication entity and
its current location, we allow entities to be mobile, enable them to be reached
by any of a number of basic communication primitives, enable communication to
span networks with different technologies and allow for disconnected operation.
Furthermore, with the ability to communicate between names, the communication
path can be dynamically bound to any of a number of end-points, and the
end-points themselves could change as needed. A key benefit of our architecture
is its ability to accommodate gradual migration from the current IP
infrastructure to a future that may be a ubiquitous Information Centric
Network. Basic building blocks of Internames are: i) a name-based Application
Programming Interface; ii) a separation of identifiers (names) and locators;
iii) a powerful Name Resolution Service (NRS) that dynamically maps names to
locators, as a function of time/location/context/service; iv) a built-in
capacity of evolution, allowing a transparent migration from current networks
and the ability to include as particular cases current specific architectures.
To achieve this vision, shared by many other researchers, we exploit and expand
on Information Centric Networking principles, extending ICN functionality
beyond content retrieval, easing send-to-name and push services, and allowing
to use names also to route data in the return path. A key role in this
architecture is played by the NRS, which allows for the co-existence of
multiple network "realms", including current IP and non-IP networks, glued
together by a name-to-name overarching communication primitive.Comment: 6 page
Route Swarm: Wireless Network Optimization through Mobility
In this paper, we demonstrate a novel hybrid architecture for coordinating
networked robots in sensing and information routing applications. The proposed
INformation and Sensing driven PhysIcally REconfigurable robotic network
(INSPIRE), consists of a Physical Control Plane (PCP) which commands agent
position, and an Information Control Plane (ICP) which regulates information
flow towards communication/sensing objectives. We describe an instantiation
where a mobile robotic network is dynamically reconfigured to ensure high
quality routes between static wireless nodes, which act as source/destination
pairs for information flow. The ICP commands the robots towards evenly
distributed inter-flow allocations, with intra-flow configurations that
maximize route quality. The PCP then guides the robots via potential-based
control to reconfigure according to ICP commands. This formulation, deemed
Route Swarm, decouples information flow and physical control, generating a
feedback between routing and sensing needs and robotic configuration. We
demonstrate our propositions through simulation under a realistic wireless
network regime.Comment: 9 pages, 4 figures, submitted to the IEEE International Conference on
Intelligent Robots and Systems (IROS) 201
The Impact of CSI and Power Allocation on Relay Channel Capacity and Cooperation Strategies
Capacity gains from transmitter and receiver cooperation are compared in a
relay network where the cooperating nodes are close together. Under
quasi-static phase fading, when all nodes have equal average transmit power
along with full channel state information (CSI), it is shown that transmitter
cooperation outperforms receiver cooperation, whereas the opposite is true when
power is optimally allocated among the cooperating nodes but only CSI at the
receiver (CSIR) is available. When the nodes have equal power with CSIR only,
cooperative schemes are shown to offer no capacity improvement over
non-cooperation under the same network power constraint. When the system is
under optimal power allocation with full CSI, the decode-and-forward
transmitter cooperation rate is close to its cut-set capacity upper bound, and
outperforms compress-and-forward receiver cooperation. Under fast Rayleigh
fading in the high SNR regime, similar conclusions follow. Cooperative systems
provide resilience to fading in channel magnitudes; however, capacity becomes
more sensitive to power allocation, and the cooperating nodes need to be closer
together for the decode-and-forward scheme to be capacity-achieving. Moreover,
to realize capacity improvement, full CSI is necessary in transmitter
cooperation, while in receiver cooperation optimal power allocation is
essential.Comment: Accepted for publication in IEEE Transactions on Wireless
Communication
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