5,379 research outputs found
M2-Brane Superalgebra from Bagger-Lambert Theory
It is known that the M2-brane worldvolume superalgebra includes two p-form
central charges that encode the M-theory intersections involving M2-branes. In
this paper we show by explicit computation that the Bagger-Lambert Lagrangian
realizes the M2-brane superalgebra, including also the central extensions.
Solitons of the Bagger-Lambert theory, that are interpreted as worldvolume
realizations of intersecting branes, are shown to saturate a BPS-bound given in
terms of the corresponding central charge.Comment: 19 pages, harvma
On the Exploitation of Admittance Measurements for Wired Network Topology Derivation
The knowledge of the topology of a wired network is often of fundamental
importance. For instance, in the context of Power Line Communications (PLC)
networks it is helpful to implement data routing strategies, while in power
distribution networks and Smart Micro Grids (SMG) it is required for grid
monitoring and for power flow management. In this paper, we use the
transmission line theory to shed new light and to show how the topological
properties of a wired network can be found exploiting admittance measurements
at the nodes. An analytic proof is reported to show that the derivation of the
topology can be done in complex networks under certain assumptions. We also
analyze the effect of the network background noise on admittance measurements.
In this respect, we propose a topology derivation algorithm that works in the
presence of noise. We finally analyze the performance of the algorithm using
values that are typical of power line distribution networks.Comment: A version of this manuscript has been submitted to the IEEE
Transactions on Instrumentation and Measurement for possible publication. The
paper consists of 8 pages, 11 figures, 1 tabl
Exact results for vortex loop operators in 3d supersymmetric theories
Three dimensional field theories admit disorder line operators, dubbed vortex
loop operators. They are defined by the path integral in the presence of
prescribed singularities along the defect line. We study half-BPS vortex loop
operators for N=2 supersymmetric theories on S^3, its deformation S^3_b and S^1
x S^2. We construct BPS vortex loops defined by the path integral with a fixed
gauge or flavor holonomy for infinitesimal curves linking the loop. It is also
possible to include a singular profile for matter fields. For vortex loops
defined by holonomy, we perform supersymmetric localization by calculating the
fluctuation modes, or alternatively by applying the index theory for
transversally elliptic operators. We clarify how the latter method works in
situations without fixed points of relevant isometries. Abelian mirror symmetry
transforms Wilson and vortex loops in a specific way. In particular an ordinary
Wilson loop transforms into a vortex loop for a flavor symmetry. Our
localization results confirm the predictions of abelian mirror symmetry.Comment: 70 pages, 3 figures; version 2: 73 pages, added references, expanded
discussions on index theory, and corrected some formulas and argument
Constructive Preference Elicitation over Hybrid Combinatorial Spaces
Preference elicitation is the task of suggesting a highly preferred
configuration to a decision maker. The preferences are typically learned by
querying the user for choice feedback over pairs or sets of objects. In its
constructive variant, new objects are synthesized "from scratch" by maximizing
an estimate of the user utility over a combinatorial (possibly infinite) space
of candidates. In the constructive setting, most existing elicitation
techniques fail because they rely on exhaustive enumeration of the candidates.
A previous solution explicitly designed for constructive tasks comes with no
formal performance guarantees, and can be very expensive in (or unapplicable
to) problems with non-Boolean attributes. We propose the Choice Perceptron, a
Perceptron-like algorithm for learning user preferences from set-wise choice
feedback over constructive domains and hybrid Boolean-numeric feature spaces.
We provide a theoretical analysis on the attained regret that holds for a large
class of query selection strategies, and devise a heuristic strategy that aims
at optimizing the regret in practice. Finally, we demonstrate its effectiveness
by empirical evaluation against existing competitors on constructive scenarios
of increasing complexity.Comment: AAAI 2018, computing methodologies, machine learning, learning
paradigms, supervised learning, structured output
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