Status of Chiral-Scale Perturbation Theory

Chiral-scale perturbation theory $\chi$PT$_\sigma$ has been proposed as an alternative to chiral $SU(3)_L\times SU(3)_R$ perturbation theory which explains the $\Delta I = 1/2$ rule for kaon decays. It is based on a low-energy expansion about an infrared fixed point in three-flavor QCD. In $\chi$PT$_\sigma$, quark condensation $\langle\bar q q \rangle_\mathrm{vac} \neq 0$ induces nine Nambu-Goldstone bosons: $\pi, K, \eta$ and a QCD dilaton $\sigma$ which we identify with the $f_0(500)$ resonance. Partial conservation of the dilatation and chiral currents constrains low-energy constants which enter the effective Lagrangian of $\chi$PT$_\sigma$. These constraints allow us to obtain new phenomenological bounds on the dilaton decay constant via the coupling of $\sigma/f_0$ to pions, whose value is known precisely from dispersive analyses of $\pi\pi$ scattering. Improved predictions for $\sigma \to \gamma \gamma$ and the $\sigma NN$ coupling are also noted. To test $\chi$PT$_\sigma$ for kaon decays, we revive a 1985 proposal for lattice methods to be applied to $K \to \pi$ on-shell.Comment: 10 pages, 1 figure. Presented at the 8th International Workshop on Chiral Dynamics, 29 June 2015 - 03 July 2015, Pisa, Italy. Revision: references and comment adde

The Aesthetic Uncanny: Staging Dorian Gray

This article discusses my theatrical adaptation of Oscar Wilde's The Picture of Dorian Gray (1891) for the Edinburgh Festival Fringe (2008). Freud's concept of the uncanny (1919) was treated as a purely aesthetic phenomenon and related to late nineteenth century social and literary preoccupations such as Christianity, the supernatural and glamorous, criminal homosexuality. These considerations led to a conceptual ground plan that allowed for experiments during rehearsal in a form of theatrical shorthand

Magnetic properties of strongly disordered electronic systems

We present a unified, global perspective on the magnetic properties of strongly disordered electronic systems, with special emphasis on the case where the ground state is metallic. We review the arguments for the instability of the disordered Fermi liquid state towards the formation of local magnetic moments, and argue that their singular low temperature thermodynamics are the ``quantum Griffiths'' precursors of the quantum phase transition to a metallic spin glass; the local moment formation is therefore not directly related to the metal-insulator transition. We also review the the mean-field theory of the disordered Fermi liquid to metallic spin glass transition and describe the separate regime of ``non-Fermi liquid'' behavior at higher temperatures near the quantum critical point. The relationship to experimental results on doped semiconductors and heavy-fermion compounds is noted.Comment: 25 pages; Contribution to the Royal Society Discussion Meeting on "The Metal-Non Metal Transition in Macroscopic and Microscopic Systems", March 5-6, 199

ΔI=1/2\Delta I=1/2 rule for kaon decays derived from QCD infrared fixed point

This article gives details of our proposal to replace ordinary chiral $SU(3)_L\times SU(3)_R$ perturbation theory $\chi$PT$_3$ by 3-flavor chiral-scale perturbation theory $\chi$PT$_\sigma$. In $\chi$PT$_\sigma$, amplitudes are expanded at low energies and small $u,d,s$ quark masses about an infrared fixed point $\alpha^{}_\mathrm{IR}$ of 3-flavor QCD. At $\alpha^{}_\mathrm{IR}$, the quark condensate $\langle \bar{q}q\rangle_{\mathrm{vac}} \not= 0$ induces nine Nambu-Goldstone bosons: $\pi, K, \eta$ and a $0^{++}$ QCD dilaton $\sigma$. Physically, $\sigma$ appears as the $f_{0}(500)$ resonance, a pole at a complex mass with real part $\lesssim m_K$. The $\Delta I=1/2$ rule for nonleptonic $K$-decays is then a consequence of $\chi$PT$_\sigma$, with a $K_S\sigma$ coupling fixed by data for $\gamma\gamma\rightarrow\pi\pi$ and $K_{S} \to \gamma\gamma$. We estimate $R_\mathrm{IR} \approx 5$ for the nonperturbative Drell-Yan ratio $R = \sigma(e^{+}e^{-}\rightarrow\mathrm{hadrons})/ \sigma(e^{+}e^{-}\rightarrow\mu^{+}\mu^{-})$ at $\alpha^{}_\mathrm{IR}$, and show that, in the many-color limit, $\sigma/f_0$ becomes a narrow $q\bar{q}$ state with planar-gluon corrections. Rules for the order of terms in $\chi$PT$_\sigma$ loop expansions are derived in Appendix A, and extended in Appendix B to include inverse-power Li-Pagels singularities due to external operators. This relates to an observation that, for $\gamma\gamma$ channels, partial conservation of the dilatation current is not equivalent to $\sigma$-pole dominance.Comment: 20 pages, 11 figures. This article is an expanded version of the letter arXiv:1203.1321 (2012). v4: Fig. 1 moved to second page to match PRD formatting, minor changes to text and reference

Metallization of Fluid Hydrogen

The electrical resistivity of liquid hydrogen has been measured at the high dynamic pressures, densities and temperatures that can be achieved with a reverberating shock wave. The resulting data are most naturally interpreted in terms of a continuous transition from a semiconducting to a metallic, largely diatomic fluid, the latter at 140 GPa, (ninefold compression) and 3000 K. While the fluid at these conditions resembles common liquid metals by the scale of its resistivity of 500 micro-ohm-cm, it differs by retaining a strong pairing character, and the precise mechanism by which a metallic state might be attained is still a matter of debate. Some evident possibilities include (i) physics of a largely one-body character, such as a band-overlap transition, (ii) physics of a strong-coupling or many-body character,such as a Mott-Hubbard transition, and (iii) processes in which structural changes are paramount.Comment: 12 pages, RevTeX format. Figures available on request; send mail to: [email protected] To appear: Philosophical Transaction of the Royal Society

Comparison of Howland and General Impedance Converter (GIC) circuit based current sources for bio-impedance measurements

The current source is a key component in bio-impedance measurement systems. The accuracy of the current source can be measured in terms of its output impedance together with other parameters, with certain applications demanding extremely high output impedance. This paper presents an investigation and comparison of different current source designs based on the Enhanced Howland circuit combined with a General Impedance Converter (GIC) circuit using both ideal and non-ideal operational amplifiers. Under differing load conditions two different settings of the GIC are evaluated and the results are compared to show its performance settings. Whilst the study has shown that over a wide bandwidth (i.e. 100Hz-100MHz) the output impedance is limited, operation over a more limited range offers output impedance in the Giga-ohm range, which can be considered as being infinite

Effects of Alternative Seating on the Academic Engagement of Children With Autism

Students with sensory integration deficits may display a hyper or hyposensitivity to sensory information and lack the ability to modulate that input in socially appropriate ways. Therapy balls as a sensory integration intervention has shown positive results for use with fourth grade students with attention deficit hyperactivity disorder and preschool children with autism. Therapy balls were used to improve classroom behavior and improve student engagement to relevant materials and persons. Therapy balls are large, inflatable balls, often used for exercise. This form of intervention is thought to afford students with autism who may have deficits in their ability to modulate sensory input the chance to do this in an appropriate way. Students can bounce or roll on the ball which aids in sensory modulation without being disruptive to instruction. The current study replicated the Schilling and Schwartz (2004) study with high school students with autism in a self-contained class. The study examined the effects of therapy balls as seating on in-seat behavior and on-task behavior. Momentary time sampling was used to ascertain the percentage of time that each participant is in-seat/on-ball and on-task/academically engaged. Participants were recruited from a local high school self-contained class for students with autism and include one male and one female student. Single-case design methodologies were used to examine the results. For each participant, data was collected in four phases, two using typical seating and two using the proposed intervention. Participant's data indicate that the therapy ball intervention was initially helpful in improving on-task behavior but that improvement was not replicated after a withdrawal of the intervention. For both participants, in-seat behavior remained appropriate and was therefore, not the focus of this intervention.  M.A