17,637 research outputs found
Augmented Superfield Approach to Gauge-invariant Massive 2-Form Theory
We discuss the complete sets of the off-shell nilpotent (i.e. s^2_{(a)b} = 0)
and absolutely anticommuting (i.e. s_b s_{ab} + s_{ab} s_b = 0)
Becchi-Rouet-Stora-Tyutin (BRST) (s_b) and anti-BRST (s_{ab}) symmetries for
the (3+1)-dimensional (4D) gauge-invariant massive 2-form theory within the
framework of augmented superfield approach to BRST formalism. In this
formalism, we obtain the coupled (but equivalent) Lagrangian densities which
respect both BRST and anti-BRST symmetries on the constrained hypersurface
defined by the Curci-Ferrari type conditions. The absolute anticommutativity
property of the (anti-)BRST transformations (and corresponding generators) is
ensured by the existence of the Curci-Ferrari type conditions which emerge very
naturally in this formalism. Furthermore, the gauge-invariant restriction plays
a decisive role in deriving the proper (anti-)BRST transformations for the
St{\"u}ckelberg-like vector field.Comment: LaTeX file, 22 pages, no figures, version to appear in Eur. Phys. J.
C (2017
Non-robustness of the Cash-in-Advance Equilibrium in the Trading-Post Model
The main justification for cash-in-advance (CIA) equilibria when there are multiple assets is a Shapley-Shubik trading-post model where the agents coordinate on a particular medium of exchange. Of course, there are other equilibria. We introduce a refinement and show that the CIA equilibrium does not satisfy our refinement while there exist equilibria that do.
Extended Conversations in Sender-Receiver Games
Aumann and Hart (Econometrica, Nov. 2003) have shown that in games of one-sided incomplete information, the set of equilibrium outcomes achievable can be expanded considerably if the players are allowed to communicate without exogenous time limits and completely characterise the equilibria from such communication. Their research provokes (at least) four questions. (i) Is it true that the set of equilibriumpayoffs stabilises (i.e. remains unchanged) if there are sufficiently many rounds of communication? (ii) Is the set of equilibria from communication which is unbounded but finite with probability one is the same as equilibria from communication which is just unbounded? (iii) Are any of these sets of equilibria “simple” and if so, is there an algorithm to compute them? (iv) Does unbounded communication (of order type w) exhaust all possibilities so that further communication is irrelevant? We show that in the context of finite Sender-Receiver games, the answer to all four is yes if the game satisfies a certain geometric condition. We then relate this condition to some geometric facts about the notion of bi-convexity and argue that if any of the questions has a negative answer then all three of the questions are likely to have a negative answer.
Iterative Soft Input Soft Output Decoding of Reed-Solomon Codes by Adapting the Parity Check Matrix
An iterative algorithm is presented for soft-input-soft-output (SISO)
decoding of Reed-Solomon (RS) codes. The proposed iterative algorithm uses the
sum product algorithm (SPA) in conjunction with a binary parity check matrix of
the RS code. The novelty is in reducing a submatrix of the binary parity check
matrix that corresponds to less reliable bits to a sparse nature before the SPA
is applied at each iteration. The proposed algorithm can be geometrically
interpreted as a two-stage gradient descent with an adaptive potential
function. This adaptive procedure is crucial to the convergence behavior of the
gradient descent algorithm and, therefore, significantly improves the
performance. Simulation results show that the proposed decoding algorithm and
its variations provide significant gain over hard decision decoding (HDD) and
compare favorably with other popular soft decision decoding methods.Comment: 10 pages, 10 figures, final version accepted by IEEE Trans. on
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