Thermodynamics of Dyonic Lifshitz Black Holes

Black holes with asymptotic anisotropic scaling are conjectured to be gravity duals of condensed matter system close to quantum critical points with non-trivial dynamical exponent z at finite temperature. A holographic renormalization procedure is presented that allows thermodynamic potentials to be defined for objects with both electric and magnetic charge in such a way that standard thermodynamic relations hold. Black holes in asymptotic Lifshitz spacetimes can exhibit paramagnetic behavior at low temperature limit for certain values of the critical exponent z, whereas the behavior of AdS black holes is always diamagnetic.Comment: 26 pages, 4 figure

Finding Fault? Divorce Law and Practice in England and Wales

This is the final version of the report. Available from Nuffield Foundation via the link in this record.1. Key messages The law of divorce in England and Wales has been subject to criticism for decades, most recently following the rare defended case of Owens v Owens. This major research study aimed to explore how the law is working in practice. The current law and use of fault The sole ground for divorce in England and Wales is the irretrievable breakdown of the marriage. But a divorce may be granted only if one of five ‘Facts’ is proved. Whilst many people might assume this is required, it is not necessary to prove that that ‘Fact’ was a cause of the breakdown. Three Facts are fault-based: adultery, behaviour, and desertion. Two Facts are based on separation: two years if the other spouse consents to divorce, five years if they do not. In 2015, 60% of English and Welsh divorces were granted on adultery or behaviour. In Scotland, where different procedural and related legal rules create different incentive structures, it was just 6%. Elsewhere, fault has been abolished or is just one option, and often a practically insignificant one, among several divorce grounds. The continuing problems of fault Academic research and Law Commission reviews from the 1970s onwards reported serious problems with the divorce law, including the lack of honesty of the system with the parties exaggerating behaviour allegations to get a quick divorce, while the court could do little more than ‘pretend’ to inquire into allegations. This study found that those problems continue and have worsened in some respects. Fault, especially behaviour, continues to be relied on to secure a faster divorce. The consequence is that parties often feel under pressure to exaggerate allegations or retro-fit the reasons for their separation into one of the legal Facts, even though the court’s expectations of what is required to make out each Fact is now actually very low, particularly for behaviour. The court has a duty to inquire into allegations but in practice in undefended cases only has the capacity to take the petitioner’s allegations at face value. That is procedurally unfair for the great majority of respondents who cannot defend themselves against the allegations. Parties embarking on the process might reasonably assume that the law is underpinned by a fault-based logic: that petitions should reflect who and what was to blame for the relationship breakdown. Yet whilst the law invites parties to rely on fault-based Facts, it does not require the court to adjudicate on responsibility in that way – not least because it will very often be impossible to allocate blame accurately in this context. Yet respondents on the receiving end of fault-based petitions inevitably feel cast as the ‘guilty’ party. The study found no evidence that fault prevents or slows down the decision to divorce and some evidence that it may shorten the time from break up to filing. We also found, as previously, that producing evidence of fault can create or exacerbate unnecessary conflict with damaging consequences for children and contrary to the thrust of family law policy. 10 The current divorce law is now nearly 50 years old. Its apparent rationale and operation are at odds with a modern, transparent, problem-solving family justice system that seeks to minimise the consequences of relationship breakdown for both adults and children. The need for law reform to finally remove fault The study shows that we already have something tantamount to immediate unilateral divorce ‘on demand’, but masked by an often painful, and sometimes destructive, legal ritual with no obvious benefits for the parties or the state. A clearer and more honest approach, that would also be fairer, more child-centred and cost-effective, would be to reform the law to remove fault entirely. We propose a notification system where divorce would be available if one or both parties register that the marriage has broken down irretrievably and that intention is confirmed by one or both parties after a minimum period of six months.Nuffield Foundatio

Black Hole Thermodynamics and Heavy Fermion Metals

Heavy fermion alloys at critical doping typically exhibit non-Fermi-liquid behavior at low temperatures, including a logarithmic or power law rise in the ratio of specific heat to temperature as the temperature is lowered. Anomalous specific heat of this type is also observed in a simple class of gravitational dual models that exhibit anisotropic scaling with dynamical critical exponent z > 1.Comment: 17 pages, 4 figures; v2: added references; v3: matches published versio

Gauss-Bonnet Black Holes and Heavy Fermion Metals

We consider charged black holes in Einstein-Gauss-Bonnet Gravity with Lifshitz boundary conditions. We find that this class of models can reproduce the anomalous specific heat of condensed matter systems exhibiting non-Fermi-liquid behaviour at low temperatures. We find that the temperature dependence of the Sommerfeld ratio is sensitive to the choice of Gauss-Bonnet coupling parameter for a given value of the Lifshitz scaling parameter. We propose that this class of models is dual to a class of models of non-Fermi-liquid systems proposed by Castro-Neto et.al.Comment: 17 pages, 6 figures, pdfLatex; small corrections to figure 10 in this versio

Light Higgsino from Axion Dark Radiation

The recent observations imply that there is an extra relativistic degree of freedom coined dark radiation. We argue that the QCD axion is a plausible candidate for the dark radiation, not only because of its extremely small mass, but also because in the supersymmetric extension of the Peccei-Quinn mechanism the saxion tends to dominate the Universe and decays into axions with a sizable branching fraction. We show that the Higgsino mixing parameter mu is bounded from above when the axions produced at the saxion decays constitute the dark radiation: mu \lesssim 300 GeV for a saxion lighter than 2m_W, and mu less than the saxion mass otherwise. Interestingly, the Higgsino can be light enough to be within the reach of LHC and/or ILC even when the other superparticles are heavy with mass about 1 TeV or higher. We also estimate the abundance of axino produced by the decays of Higgsino and saxion.Comment: 18 pages, 1 figure; published in JHE

Quantization of Integrable Systems and a 2d/4d Duality

We present a new duality between the F-terms of supersymmetric field theories defined in two- and four-dimensions respectively. The duality relates N=2 supersymmetric gauge theories in four dimensions, deformed by an Omega-background in one plane, to N=(2,2) gauged linear sigma-models in two dimensions. On the four dimensional side, our main example is N=2 SQCD with gauge group SU(L) and 2L fundamental flavours. Using ideas of Nekrasov and Shatashvili, we argue that the Coulomb branch of this theory provides a quantization of the classical Heisenberg SL(2) spin chain. Agreement with the standard quantization via the Algebraic Bethe Ansatz implies the existence of an isomorphism between the chiral ring of the 4d theory and that of a certain two-dimensional theory. The latter can be understood as the worldvolume theory on a surface operator/vortex string probing the Higgs branch of the same 4d theory. We check the proposed duality by explicit calculation at low orders in the instanton expansion. One striking consequence is that the Seiberg-Witten solution of the 4d theory is captured by a one-loop computation in two dimensions. The duality also has interesting connections with the AGT conjecture, matrix models and topological string theory where it corresponds to a refined version of the geometric transition.Comment: 51 pages, 7 figures. Additional comments, minor improvements and references adde

Soliton pair creation in classical wave scattering

We study classical production of soliton-antisoliton pairs from colliding wave packets in (1+1)-dimensional scalar field model. Wave packets represent multiparticle states in quantum theory; we characterize them by energy E and particle number N. Sampling stochastically over the forms of wave packets, we find the entire region in (E,N) plane which corresponds to classical creation of soliton pairs. Particle number is parametrically large within this region meaning that the probability of soliton-antisoliton pair production in few-particle collisions is exponentially suppressed.Comment: 16 pages, 8 figures, journal version; misprint correcte

Three-dimensional jamming and flows of soft glassy materials

Various disordered dense systems such as foams, gels, emulsions and colloidal suspensions, exhibit a jamming transition from a liquid state (they flow) to a solid state below a yield stress. Their structure, thoroughly studied with powerful means of 3D characterization, exhibits some analogy with that of glasses which led to call them soft glassy materials. However, despite its importance for geophysical and industrial applications, their rheological behavior, and its microscopic origin, is still poorly known, in particular because of its nonlinear nature. Here we show from two original experiments that a simple 3D continuum description of the behaviour of soft glassy materials can be built. We first show that when a flow is imposed in some direction there is no yield resistance to a secondary flow: these systems are always unjammed simultaneously in all directions of space. The 3D jamming criterion appears to be the plasticity criterion encountered in most solids. We also find that they behave as simple liquids in the direction orthogonal to that of the main flow; their viscosity is inversely proportional to the main flow shear rate, as a signature of shear-induced structural relaxation, in close similarity with the structural relaxations driven by temperature and density in other glassy systems.Comment: http://www.nature.com/nmat/journal/v9/n2/abs/nmat2615.htm

Feasibility of offering nicotine replacement therapy as a relapse prevention treatment in routine smoking cessation services

Background: National Health Service stop smoking services (NHS SSS) in the UK offer cost- effective smoking cessation services. Despite high abstinence rates after acute cessation treatment, the majority of clients have relapsed by one year. Several interventions have been identified, from trial data, as effective in preventing relapse to smoking. This study investigated uptake, feasibility and acceptability of offering nicotine replacement therapy (NRT) as a relapse prevention intervention (RPI) in NHS SSS. Methods: Eligible smokers who had successfully completed acute cessation treatment using NRT at Nottingham City NHS SSS between April 2010 and January 2011 were offered the RPI and the rate of uptake was monitored. Consenting individuals completed a baseline questionnaire, providing demographic and smoking behaviour data. The RPI consisted of using NRT for a further 12 weeks after initial cessation-orientated treatment had ended. At a six-month review, self-reported smoking status was assessed via telephone. Anonymised demographic data on NHS SSS users who did not agree to participate in the study were retrieved from NHS SSS records and used to determine the presence of any socio-demographic differences between individuals who agreed to participate in the study and those who did not. Semi-structured telephone interviews were conducted with a selection of participants; these were audio-recorded, transcribed and analysed to identify participants’ views on the RPI. Results: Of 493 stop smoking service clients who were assessed, 260 were eligible for and offered the RPI and 115 (44%, CI 38%- 50%) accepted. Individuals who accepted NRT were significantly more likely to be older (p < 0.001) and to pay for their prescriptions (p < 0.001). Quitters who had never worked or were unemployed were significantly less likely to accept the offer of relapse prevention compared to those in routine and manual occupations (55% reduction in odds, p = 0.026). Interview findings revealed that clients who accepted extended NRT felt the longer duration of pharmacological and psychological support were both valuable in helping them to remain abstinent. Conclusion: In routine smoking cessation service care, it is feasible to offer clients extended courses of NRT as a RPI. The RPI was acceptable to them as almost half of the eligible clients offered this treatment accepted it. Keywords: Smoking relapse prevention, Nicotine replacement therapy, Feasibility study, Smoking cessation servic