Holographic bulk viscosity: GPR vs EO

Recently Eling and Oz (EO) proposed a formula for the holographic bulk viscosity, in arXiv:1103.1657, derived from the null horizon focusing equation. This formula seems different from that obtained earlier by Gubser, Pufu and Rocha (GPR) in arXiv:0806.0407 calculated from the IR limit of the two-point function of the trace of the stress tensor. The two were shown to agree only for some simple scaling cases. We point out that the two formulae agree in two non-trivial holographic theories describing RG flows. The first is the strongly coupled N=2* gauge theory plasma. The second is the semi-phenomenological model of Improved Holographic QCD.Comment: 21 pages, 2 figure

ERA distribution of information systems journals

The Excellence in Research for Australia (ERA) initiative being conducted by the Australian Research Council (ARC), mandates a single journal and conference ranking scheme over every academic discipline in Australia. A universal publication outlet ranking list mandated by a government agency is unique and has attracted interest and comment both within Australia and overseas. Equally, the interest shown has come from all sectors involved in academic publishing &ndash; authors, reviewers, publishers &ndash; and from commercial and open access publishers. This paper investigates the distribution of information systems journals over the various ERA parameters and comments on a claim of bias whereby the ranking of a journal is positively influenced by the number of years it has been in existence in the areas of information systems and business journals. Clear evidence of the diversity of the information systems discipline is observed. The benefits of a multidisciplinary foundation for information systems is also noted. Longer established journals are shown to attract higher rankings and possible reasons for and implications flowing from this are discussed.<br /

A note on dual giant gravitons in AdS4×CP3AdS_{4}\times \mathbb{CP}^{3}

We study some of the properties of dual giant gravitons - D2-branes wrapped on an $S^{2}\subset AdS_{4}$ - in type IIA string theory on $AdS_{4}\times \mathbb{CP}^{3}$. In particular we confirm that the spectrum of small fluctuations about the giant is both real and independent of the size of the graviton. We also extend previously developed techniques for attaching open strings to giants to this D2-brane giant and focus on two particular limits of the resulting string sigma model: In the pp-wave limit we quantize the string and compute the spectrum of bosonic excitations while in the semiclassical limit, we read off the fast string Polyakov action and comment on the comparison to the Landau-Lifshitz action for the dual open spin chain.Comment: v3 significantly changed: added coupling to RR 1-form and turned on worldvolume gauge field, computed gauge field fluctuation, added comments on closure of the sl(2) sector and re-written to improve clarity. This version published in JHE

OPTIMASS: A Package for the Minimization of Kinematic Mass Functions with Constraints

Reconstructed mass variables, such as $M_2$, $M_{2C}$, $M_T^\star$, and $M_{T2}^W$, play an essential role in searches for new physics at hadron colliders. The calculation of these variables generally involves constrained minimization in a large parameter space, which is numerically challenging. We provide a C++ code, OPTIMASS, which interfaces with the MINUIT library to perform this constrained minimization using the Augmented Lagrangian Method. The code can be applied to arbitrarily general event topologies and thus allows the user to significantly extend the existing set of kinematic variables. We describe this code and its physics motivation, and demonstrate its use in the analysis of the fully leptonic decay of pair-produced top quarks using the $M_2$ variables.Comment: 39 pages, 12 figures, (1) minor revision in section 3, (2) figure added in section 4.3, (3) reference added and (4) matched with published versio

Beyond the Planar Limit in ABJM

In this article we consider gauge theories with a U(N)X U(N) gauge group. We provide, for the first time, a complete set of operators built from scalar fields that are in the bi fundamental of the two groups. Our operators diagonalize the two point function of the free field theory at all orders in 1/N. We then use this basis to investigate non-planar anomalous dimensions in the ABJM theory. We show that the dilatation operator reduces to a set of decoupled harmonic oscillators, signaling integrability in a nonplanar large N limit.Comment: v2: minor revisison

Complexity and phase transitions in a holographic QCD model

Applying the "Complexity=Action" conjecture, we study the holographic complexity close to crossover/phase transition in a holographic QCD model proposed by Gubser et al. This model can realize three types of phase transition, crossover or first and second order, depending on the parameters of the dilaton potential. The re-scaled late-time growth rate of holographic complexity density for the three cases is calculated. Our results show that it experiences a fast drop/jump close to the critical point while approaching constants far beyond the critical temperature. Moreover, close to the critical temperature, it shows a behavior characterizing the type of the transition. These features suggest that the growth rate of the holographic complexity may be used as a good parameter to characterize the phase transition. The Lloyd's bound is always satisfied for the cases we considered but only saturated for the conformal case.Comment: v1: 14 pages, 2 figures; v2: refs added, minor modifications. arXiv admin note: substantial text overlap with arXiv:1608.03072; v3: More details on the Lloyd's bound, matching the published versio

Unitarity-Cuts, Stokes' Theorem and Berry's Phase

Two-particle unitarity-cuts of scattering amplitudes can be efficiently computed by applying Stokes' Theorem, in the fashion of the Generalised Cauchy Theorem. Consequently, the Optical Theorem can be related to the Berry Phase, showing how the imaginary part of arbitrary one-loop Feynman amplitudes can be interpreted as the flux of a complex 2-form.Comment: presented at RADCOR 2009 - 9th International Symposium on Radiative Corrections, October 25 - 30 2009, Ascona, Switzerlan