Impact of dynamical chiral symmetry breaking on meson structure and interactions

We provide a glimpse of recent progress in meson physics made via QCD's Dyson-Schwinger equations with: a perspective on confinement and dynamical chiral symmetry breaking (DCSB); a pre'cis on the physics of in-hadron condensates; results for the masses of the \pi, \sigma, \rho, a_1 mesons and their first-radial excitations; and an illustration of the impact of DCSB on the pion form factor.Comment: 6 pages, 3 figures, 1 table. Contribution to Proceedings of the 11th International Workshop on Meson Production, Properties and Interaction, Uniwersytet Jagiellonski, Instytut Fizyki, Krakow, Poland, 10-15 June 201

Towards the graviton from spinfoams: the 3d toy model

Recently, a proposal has appeared for the extraction of the 2-point function of linearised quantum gravity, within the spinfoam formalism. This relies on the use of a boundary state, which introduces a semi-classical flat geometry on the boundary. In this paper, we investigate this proposal considering a toy model in the (Riemannian) 3d case, where the semi-classical limit is better understood. We show that in this limit the propagation kernel of the model is the one for the harmonic oscillator. This is at the origin of the expected 1/L behaviour of the 2-point function. Furthermore, we numerically study the short scales regime, where deviations from this behaviour occur.Comment: 8 pages, 2 figures; v3 revised versio

Electromagnetic properties of ground and excited state pseudoscalar mesons

The axial-vector Ward-Takahashi identity places constraints on particular properties of every pseudoscalar meson. For example, in the chiral limit all pseudoscalar mesons, except the Goldstone mode, decouple from the axial-vector current. Nevertheless, all neutral pseudoscalar mesons couple to two photons. The strength of the \pi_n^0 \gamma \gamma coupling, where n=0 denotes the Goldstone mode, is affected by the Abelian anomaly's continuum contribution. The effect is material for n \neq 0. The \gamma* \pi_n \gamma* transition form factor, T_{\pi_n}(Q^2), is nonzero for all n, and T_{\pi_n}(Q^2) \approx (4\pi^2/3) (f_{\pi_n}/Q^2) at large Q^2. For all pseudoscalars but the Goldstone mode, this leading contribution vanishes in the chiral limit. In this instance the ultraviolet power-law behaviour is 1/Q^4 for n \neq 0, and we find numerically T_{\pi_1}(Q^2) \simeq (4\pi^2/3) (-/Q^4). This subleading power-law behaviour is always present. In general its coefficient is not simply related to f_{\pi_n}. The properties of n \neq 0 pseudoscalar mesons are sensitive to the pointwise behaviour of the long-range piece of the interaction between light-quarks.Comment: 13 pages, 5 figure

CLTs and asymptotic variance of time-sampled Markov chains

For a Markov transition kernel P and a probability distribution μ on nonnegative integers, a time-sampled Markov chain evolves according to the transition kernel Pμ = Σkμ(k)Pk. In this note we obtain CLT conditions for time-sampled Markov chains and derive a spectral formula for the asymptotic variance. Using these results we compare efficiency of Barker's and Metropolis algorithms in terms of asymptotic variance

Two flavor color superconductivity in nonlocal chiral quark models

We study the competence between chiral symmetry restoration and two flavor color superconductivity (2SC) using a relativistic quark model with covariant nonlocal interactions. We consider two different nonlocal regulators: a Gaussian regulator and a Lorentzian regulator. We find that although the phase diagrams are qualitative similar to those obtained using models with local interactions, in our case the superconducting gaps at medium values of the chemical potential are larger. Consequently, we obtain that in that region the critical temperatures for the disappearance of the 2SC phase might be of the order of 100-120 MeV. We also find that for ratios of the quark-quark and quark-antiquark couplings somewhat above the standard value 3/4, the end point and triple point in the $T-\mu$ phase diagram meet and a phase where both the chiral and diquark condensates are non-negligible appears.Comment: 15 pages incl. 5 Postscript figure

Flaring Activity of Sgr A*: Expanding Hot Blobs

Sgr A* is considered to be a massive black hole at the Galactic center and is known to be variable in radio, millimeter, near-IR and X-rays. Recent multi-wavelength observing campaigns show a simultaneous X-ray and near-IR flare, as well as sub-millimeter and near-IR flares from Sgr A*. The flare activity is thought to be arising from the innermost region of Sgr A*. We have recently argued that the duration of flares in near-IR and submillimeter wavelengths implies that the burst of emission expands and cools on a dynamical time scale before the flares leave Sgr A*. The detection of radio flares with a time delay in the range of 20 and 40 minutes between 7 and 12mm peak emission implies adiabatic expansion of a uniform, spherical hot blob due to flare activity. We suspect that this simple outflow picture shows some of the characteristics that are known to take place in microquasars, thus we may learn much from comparative study of Sgr A* and its environment vs. microquasars.Comment: 10 pages, 5 figures, to be published in IV Microquasar Workshop: Microquasars and Beyond, September 18-22 2006, Como, Ital

Pre-pregnancy predictors of hypertension in pregnancy among Aboriginal and Torres Strait Islander women in north Queensland, Australia; a prospective cohort study

BACKGROUND Compared to other Australian women, Indigenous women are frequently at greater risk for hypertensive disorders of pregnancy. We examined pre-pregnancy factors that may predict hypertension in pregnancy in a cohort of Aboriginal and Torres Strait Islander women in north Queensland. METHODS Data on a cohort of 1009 Indigenous women of childbearing age (15–44 years) who participated in a 1998–2000 health screening program in north Queensland were combined with 1998–2008 Queensland hospitalisations data using probabilistic data linkage. Data on the women in the cohort who were hospitalised for birth (n = 220) were further combined with Queensland perinatal data which identified those diagnosed with hypertension in pregnancy. RESULTS Of 220 women who gave birth, 22 had hypertension in the pregnancy after their health check. The mean age of women with and without hypertension was similar (23.7 years and 23.9 years respectively) however Aboriginal women were more affected compared to Torres Strait Islanders. Pre-pregnancy adiposity and elevated blood pressure at the health screening program were predictors of a pregnancy affected by hypertension. After adjusting for age and ethnicity, each 1 cm increase in waist circumference showed a 4% increased risk for hypertension in pregnancy (PR 1.04; 95% CI; 1.02-1.06); each 1 point increase in BMI showed a 9% adjusted increase in risk (1.09; 1.04-1.14). For each 1 mmHg increase in baseline systolic blood pressure there was an age and ethnicity adjusted 6% increase in risk and each 1 mmHg increase in diastolic blood pressure showed a 7% increase in risk (1.06; 1.03-1.09 and 1.07; 1.03-1.11 respectively). Among those free of diabetes at baseline, the presence of the metabolic syndrome (International Diabetes Federation criteria) predicted over a three-fold increase in age-ethnicity-adjusted risk (3.5; 1.50-8.17). CONCLUSIONS Pre-pregnancy adiposity and features of the metabolic syndrome among these young Aboriginal and Torres Strait Islander women track strongly to increased risk of hypertension in pregnancy with associated risks to the health of babies.Sandra K Campbell, John Lynch, Adrian Esterman and Robyn McDermot

Entanglement between photons and atoms coupled out from a Bose-Einstein-Condensate

We study the limitations to the relative number squeezing between photons and atoms coupled out from a homogeneous Bose-Einstein-Condensate. We consider the coupling between the translational atomic states by two photon Bragg processes, with one of the photon modes involved in the Bragg process in a coherent state, and the other initially unpopulated. We start with an interacting Bose- condensate at zero temperature and compute the time evolution for the system. We study the squeezing, i.e. the variance of the occupation number difference between the second photon and the atomic c.m. mode. We discuss how collisions between the atoms and photon rescattering affect the degree of squeezing which may be reached in such experiments.Comment: 4 pages RevTeX, 3 figure

Searching for physics beyond the Standard Model through the dipole interaction

The magnetic dipole interaction played a central role in the development of QED, and continued in that role for the Standard Model. The muon anomalous magnetic moment has served as a benchmark for models of new physics, and the present experimental value is larger than the standard-model value by more than three standard deviations. The electric dipole moment (EDM) violates parity ({$P$}) and time-reversal ({$T$}) symmetries, and in the context of the $CPT$ theorem, the combination of charge conjugation and parity ($CP$). Since a new source of {$CP$} violation outside of that observed in the $K$ and $B$ meson systems is needed to help explain the baryon asymmetry of the universe, searches for EDMs are being carried out worldwide on a number of systems. The standard-model value of the EDM is immeasurably small, so any evidence for an EDM would signify the observation of new physics. Unique opportunities exist for EDM searches using polarized proton, deuteron or muon beams in storage rings. This talk will provide an overview of the theory of dipole moments, and the relevant experiments. The connection to the transition dipole moment that could produce lepton flavor violating interactions such as $\mu^+ \rightarrow e^+ \gamma$ is also mentioned.Comment: Invited Plenary talk at the 19th International Spin Physics Symposium, Juelic