The (11112) model on a 1+1 dimensional lattice

We study the chiral gauge model (11112) of four left-movers and one right-mover with strong interactions in the 1+1 dimensional lattice. Exact computations of relevant $S$-matrix elements demonstrate a loophole that so constructed model and its dynamics can possibly evade the ``no-go'' theorem of Nielsen and Ninomiya.Comment: 15 pages, 1 fig. to appear in Phys. Rev.

Classical simulation of commuting quantum computations implies collapse of the polynomial hierarchy

We consider quantum computations comprising only commuting gates, known as IQP computations, and provide compelling evidence that the task of sampling their output probability distributions is unlikely to be achievable by any efficient classical means. More specifically we introduce the class post-IQP of languages decided with bounded error by uniform families of IQP circuits with post-selection, and prove first that post-IQP equals the classical class PP. Using this result we show that if the output distributions of uniform IQP circuit families could be classically efficiently sampled, even up to 41% multiplicative error in the probabilities, then the infinite tower of classical complexity classes known as the polynomial hierarchy, would collapse to its third level. We mention some further results on the classical simulation properties of IQP circuit families, in particular showing that if the output distribution results from measurements on only O(log n) lines then it may in fact be classically efficiently sampled.Comment: 13 page

Stepwise Thinking in Strategic Games with Incomplete Information

This paper proposes a general incomplete information framework for studying behavior in strategic games with stepwise (viz. `level-k' or `cognitive hierarchy') thinking, which has been found to describe strategic behavior well in experiments involving players' initial responses to games. It is shown that there exist coherent stepwise beliefs, implied by step types, that have the potential to encode all relevant information. In the structure of stepwise beliefs, players are unaware of opponents doing at least as much thinking as themselves. As a result, there exists a Bayesian Nash equilibrium strategy profile in which any player at some step fixes the best responses of opponents at lower steps and then best responds herself.game theory; interactive epistemology; unawareness; Bayesian Nash equilibrium; bounded rationality; level-k; cognitive hierarchy

Kochen-Specker theorem as a precondition for secure quantum key distribution

We show that (1) the violation of the Ekert 91 inequality is a sufficient condition for certification of the Kochen-Specker (KS) theorem, and (2) the violation of the Bennett-Brassard-Mermin 92 (BBM) inequality is, also, a sufficient condition for certification of the KS theorem. Therefore the success in each QKD protocol reveals the nonclassical feature of quantum theory, in the sense that the KS realism is violated. Further, it turned out that the Ekert inequality and the BBM inequality are depictured by distillable entanglement witness inequalities. Here, we connect the success in these two key distribution processes into the no-hidden-variables theorem and into witness on distillable entanglement. We also discuss the explicit difference between the KS realism and Bell's local realism in the Hilbert space formalism of quantum theory.Comment: 4 pages, To appear in Phys. Rev.

A model for J/ψJ/\psi - kaon cross section

We calculate the cross section for the dissociation of $J/\psi$ by kaons within the framework of a meson exchange model. We find that, depending on the values of the coupling constants used, the cross section can vary from 5 mb to 30 mb at $\sqrt{s}\sim5$ GeV.Comment: 4 pages, 3 eps figure

Outcomes and costs of penetrating trauma injury in England and Wales

The official published version of the article can be found at the link below.Background: Penetrating trauma injury is generally associated with higher short-term mortality than blunt trauma, and results in substantial societal costs given the young age of those typically injured. Little information exists on the patient and treatment characteristics for penetrating trauma in England and Wales, and the acute outcomes and costs of care have not been documented and analysed in detail.Methods: Using the Trauma Audit Research Network (TARN) database, we examined patient records for persons aged 18+ years hospitalised for penetrating trauma injury between January 2000 and December 2005. Patients were stratified by injury severity score (ISS).Results: 1365 patients were identified; 16% with ISS 1-8, 50% ISS 9-15, 15% ISS 16-24, 16% ISS 25-34, and 4% with ISS 35-75. The median age was 30 years and 91% of patients were men. Over 90% of the injuries occurred in alleged assaults. Stabbings were the most common cause of injury (73%), followed by shootings (19%). Forty-seven percent were admitted to critical care for a median length of stay of 2 days; median total hospital length of stay was 7 days. Sixty-nine percent of patients underwent at least one surgical procedure. Eight percent of the patients died before discharge, with a mean time to death of 1.6 days (S.D. 4.0). Mortality ranged from 0% among patients with ISS 1-8 to 55% in patients with ISS > 34. The mean hospital cost per patient was 7983 pound, ranging from 6035 pound in patients with ISS 9-15 to El 6,438 among patients with ISS > 34. Costs varied significantly by ISS, hospital mortality, cause and body region of injury.Conclusion: The acute treatment costs of penetrating trauma injury in England and Wales vary by patient, injury and treatment characteristics. Measures designed toreduce the incidence and severity of penetrating trauma may result in significant hospital cost savings. (C) 2008 Elsevier Ltd. All rights reserved.This study was funded by Novo Nordisk A/S

Error Analysis For Encoding A Qubit In An Oscillator

In the paper titled "Encoding A Qubit In An Oscillator" Gottesman, Kitaev, and Preskill [quant-ph/0008040] described a method to encode a qubit in the continuous Hilbert space of an oscillator's position and momentum variables. This encoding provides a natural error correction scheme that can correct errors due to small shifts of the position or momentum wave functions (i.e., use of the displacement operator). We present bounds on the size of correctable shift errors when both qubit and ancilla states may contain errors. We then use these bounds to constrain the quality of input qubit and ancilla states.Comment: 5 pages, 8 figures, submitted to Physical Review