Isotropy of the early universe from CMB anisotropies

The acoustic peak in the CMB power spectrum is sensitive to causal processes and cosmological parameters in the early universe up to the time of last scattering. We provide limits on correlated spatial variations of the peak height and peak position and interpret these as constraints on the spatial variation of the cosmological parameters (baryon density, cold dark matter density and cosmological constant as well as the amplitude and tilt of the original fluctuations). We utilize recent work of Hansen, Banday and Gorski (HBG) who have studied the spatial isotropy of the power spectrum as measured by WMAP by performing the power spectrum analysis on smaller patches of the sky. We find that there is no statistically significant correlated asymmetry of the peak. HBG have also provided preliminary indications of a preferred direction in the lower angular momentum range(~ 2-40) and we show how possible explanations of this asymmetry are severely constrained by the data on the acoustic peak. Finally we show a possible non-gaussian feature in the data, associated with a difference in the northern and southern galactic hemispheres.Comment: 14 pages, 3 figures, v.2 adds an extra relevant reference and commen

Baryon Masses in Chiral Perturbation Theory with Infrared Regularization

The baryon masses are examined in SU(3) chiral perturbation theory to third order using the recently proposed infrared regularization scheme. Fourth order is estimated by evaluating the dominant diagram. With this regularization the magnitude of the loop integrals is reduced so that the convergence of the series appears to be better than in the heavy baryon approach.Comment: The original third order calculation is supplemented by an estimate of fourth order using just the dominant diagram. The convergence still appears to be better than in the heavy baryon approach. To be published in Phys. Rev. C. 15 pages latex, 2 postscript figure

Cosmological Consequences of String Axions

Axion fluctuations generated during inflation lead to isocurvature and non-Gaussian temperature fluctuations in the cosmic microwave background radiation. Following a previous analysis for the model independent string axion we consider the consequences of a measurement of these fluctuations for two additional string axions. We do so independent of any cosmological assumptions except for the axions being massless during inflation. The first axion has been shown to solve the strong CP problem for most compactifications of the heterotic string while the second axion, which does not solve the strong CP problem, obeys a mass formula which is independent of the axion scale. We find that if gravitational waves interpreted as arising from inflation are observed by the PLANCK polarimetry experiment with a Hubble constant during inflation of H_inf \apprge 10^13 GeV the existence of the first axion is ruled out and the second axion cannot obey the scale independent mass formula. In an appendix we quantitatively justify the often held assumption that temperature corrections to the zero temperature QCD axion mass may be ignored for temperatures T \apprle \Lambda_QCD.Comment: 27 pages, 4 figures; v2: References corrected; v3: Assumptions simplified, minor corrections, conclusions unchange

Final state rescattering as a contribution to B→ργB \to \rho \gamma

We provide a new estimate of the long-distance component to the radiative transition $B \to \rho \gamma$. Our mechanism involves the soft-scattering of on-shell hadronic products of nonleptonic $B$ decay, as in the chain $B \to \rho\rho \to \rho\gamma$. We employ a phenomenological fit to scattering data to estimate the effect. The specific intermediate states considered here modify the $B \to \rho \gamma$ decay rate at roughly the $5 \to 8$ level, although the underlying effect has the potential to be larger. Contrary to other mechanisms of long distance physics which have been discussed in the literature, this yields a non-negligible modification of the $B^0 \to \rho^0 \gamma$ channel and hence will provide an uncertainty in the extraction of $V_{td}$. This mechanism also affects the isospin relation between the rates for $B^- \to \rho^-\gamma$ and $B^0 \to \rho^0 \gamma$ and may generate CP asymmetries at experimentally observable levels.Comment: 15 pages, RevTex, 3 figure

Weak Hyperon Decays: Quark Sea and SU(3) Symmetry Breaking

An explanation of the difference in the values of the apparent $f/d$ ratios for the S- and P- wave amplitudes of nonleptonic hyperon decays is proposed. The argument is formulated in the framework of the standard pole model with $(56,0^{+})$ ground-state and $(70,1^{-})$ excited baryons as intermediate states for the P- and S- waves respectively. Under the assumption that the dominant part of the deviation of $(f/d)_{P-wave}$ from $-1$ is due to large quark sea effects, $SU(3)$ symmetry breaking in energy denominators is shown to lead to a prediction for $(f/d)_{S-wave}$ which is in excellent agreement with experiment. This corroborates our previous unitarity calculations which indicated that the matrix elements $$ of the parity conserving weak Hamiltonian between the ground-state baryons are characterized by $f_{0}/d_{0} \approx -1.6$ or more. A brief discussion of the problem of the relative size of S- and P- wave amplitudes is given. Finally, implications for weak radiative hyperon decays are also discussed.Comment: 26 pages, LATEX, 1647/PH IFJ Krako

Photon-Photon Scattering, Pion Polarizability and Chiral Symmetry

Recent attempts to detect the pion polarizability via analysis of $\gamma\gamma\rightarrow\pi\pi$ measurements are examined. The connection between calculations based on dispersion relations and on chiral perturbation theory is established by matching the low energy chiral amplitude with that given by a full dispersive treatment. Using the values for the polarizability required by chiral symmetry, predicted and experimental cross sections are shown to be in agreement.Comment: 21 pages(+10 figures available on request), LATEX, UMHEP-38

The Electromagnetic Mass Differences of Pions and Kaons

We use the Cottingham method to calculate the pion and kaon electromagnetic mass differences with as few model dependent inputs as possible. The constraints of chiral symmetry at low energy, QCD at high energy and experimental data in between are used in the dispersion relation. We find excellent agreement with experiment for the pion mass difference. The kaon mass difference exhibits a strong violation of the lowest order prediction of Dashen's theorem, in qualitative agreement with several other recent calculations.Comment: 40 pages, Latex, needs axodraw. and psfig. macros, 4 figure

On the Ultraviolet Behaviour of Newton's constant

We clarify a point concerning the ultraviolet behaviour of the Quantum Field Theory of gravity, under the assumption of the existence of an ultraviolet Fixed Point. We explain why Newton's constant should to scale like the inverse of the square of the cutoff, even though it is technically inessential. As a consequence of this behaviour, the existence of an UV Fixed Point would seem to imply that gravity has a built-in UV cutoff when described in Planck units, but not necessarily in other units.Comment: 8 pages; CQG class; minor changes and rearrangement

The Mixed Vector Current Correlator <0|T(V^3_\mu V^8_\nu )|0> To Two Loops in Chiral Perturbation Theory

The isospin-breaking correlator of the product of flavor octet vector currents, $V^3_\mu$ and $V^8_\nu$, $\Pi^{38}_{\mu\nu}(q^2)$ is computed to next-to-next- to-leading (two-loop) order in Chiral Perturbation Theory. Large corrections to both the magnitude and $q^2$-dependence of the one-loop result are found, and the reasons for the slow convergence of the chiral series for the correlator given. The two-loop expression involves a single ${\cal O}(q^6)$ counterterm, present also in the two-loop expressions for $\Pi^{33}_{\mu\nu}(q^2)$ and $\Pi^{88}_{\mu\nu}(q^2)$, which counterterm contributes a constant to the scalar correlator $\Pi^{38}(q^2)$. The feasibility of extracting the value of this counterterm from other sources is discussed. Analysis of the slope of the correlator with respect to $q^2$ using QCD sum rules is shown to suggest that, even to two-loop order, the chiral series for the correlator may not yet be well-converged.Comment: 32 pages, uses REVTEX and epsfig.sty with 7 uuencoded figures. Entire manuscript available as a ps file at http://www.physics.adelaide.edu.au/theory/home.html Also available via anonymous ftp at ftp://adelphi.adelaide.edu.au/pub/theory/ADP-95-27.T181.p

Strangeness Production Incorporating Chiral Symmetry

Chiral symmetry is known to be decisive for an understanding of the low energy sector of strong interactions. It is thus important for a model of relativistic heavy ion collisions to incorporate the dynamical breaking and restoration of chiral symmetry. Thus we study an expansion scenario for a quark-meson plasma using the Nambu--Jona-Lasinio (NJL) model in its three flavor version. The equations of motion for light and strange quarks as well as for pions, kaons and etas are solved using a QMD type algorithm, which is based on a parametrization of the Wigner function. The scattering processes incorporated into this calculation are of the types qq qq, q\bar q q\bar q, q\bar q MM and M q\bar q.Comment: Talk presented at the 4th International Symposium on Strangeness in Quark Matter, Padova, Italy, July 20--2