1,316 research outputs found

    Gauges and Cosmological Backreaction

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    We present a formalism for spatial averaging in cosmology applicable to general spacetimes and coordinates, and allowing the easy incorporation of a wide variety of matter sources. We apply this formalism to a Friedmann-LeMaitre-Robertson-Walker universe perturbed to second-order and present the corrections to the background in an unfixed gauge. We then present the corrections that arise in uniform curvature and conformal Newtonian gauges.Comment: 13 pages. Updated: reference added, typos corrected, exposition clarified. Version 3: Replaced with version published by JCA

    The Light-Cone Wave Function of the Pion

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    The light-cone wave function of the pion is calculated within the Nambu-Jona-Lasinio model. The result is used to derive the pion electromagnetic form factor, charge radius, structure function, pi-gamma transition form factor and distribution amplitude.Comment: 6 pages, 1 figure, elsart.sty; talk given at 10th International Light-Cone Meeting on Nonperturbative QCD and Hadron Phenomenology, Heidelberg, Germany, June 200

    Chiral Anomaly Effects and the BaBar Measurements of the γγπ0\gamma\gamma^{*}\to \pi^{0} Transition Form Factor

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    The recent BaBar measurements of the γγπ0\gamma\gamma^{*}\to \pi^{0} transition form factor show spectacular deviation from perturbative QCD prediction for large space-like Q2Q^{2} up to 34GeV234\,\rm GeV^{2}. When plotted against Q2Q^{2}, Q2F(Q2)Q^{2}F(Q^{2}) shows steady increase with Q2Q^{2} in contrast with the flat Q2Q^{2} behavior predicted by perturbative QCD, and at 34GeV234\,\rm GeV^{2} is more than 50% larger than the QCD prediction. Stimulated by the BaBar measurements, we revisit our previous paper on the cancellation of anomaly effects in high energy processes Z0π0γZ^{0}\to \pi^{0}\gamma, e+eπ0γe^{+}e^{-}\to \pi^{0}\gamma and apply our results to the γγπ0\gamma^{*}\gamma\to \pi^{0} transition form factor measured in the e+ee+eπ0e^{+}e^{-}\to e^{+}e^{-}\pi^{0} process with one highly virtual photon. We find that, the transition form factor F(Q2)F(Q^{2}) behaves as (m2Q2)×(ln(Q2/m2))2(\frac{m^{2}}{Q^{2}})\times (\ln(Q^{2}/m^{2}))^{2} and produces a striking agreement with the BaBar data for Q2F(Q2)Q^{2}F(Q^{2}) with m=132MeVm=132\,\rm MeV which also reproduces very well the CLEO data at lower Q2Q^{2}.Comment: v4, LaTeX, 8 pages, one figure, minor changes(references), to appear in Int. J. Mod. Phys.

    Donaldson-Thomas invariants and wall-crossing formulas

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    Notes from the report at the Fields institute in Toronto. We introduce the Donaldson-Thomas invariants and describe the wall-crossing formulas for numerical Donaldson-Thomas invariants.Comment: 18 pages. To appear in the Fields Institute Monograph Serie

    A Construction of Solutions to Reflection Equations for Interaction-Round-a-Face Models

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    We present a procedure in which known solutions to reflection equations for interaction-round-a-face lattice models are used to construct new solutions. The procedure is particularly well-suited to models which have a known fusion hierarchy and which are based on graphs containing a node of valency 11. Among such models are the Andrews-Baxter-Forrester models, for which we construct reflection equation solutions for fixed and free boundary conditions.Comment: 9 pages, LaTe

    Solution of the dual reflection equation for An1(1)A^{(1)}_{n-1} SOS model

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    We obtain a diagonal solution of the dual reflection equation for elliptic An1(1)A^{(1)}_{n-1} SOS model. The isomorphism between the solutions of the reflection equation and its dual is studied.Comment: Latex file 12 pages, added reference

    Information on the Pion Distribution Amplitude from the Pion-Photon Transition Form Factor with the Belle and BaBar Data

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    The pion-photon transition form factor (TFF) provides strong constraints on the pion distribution amplitude (DA). We perform an analysis of all existing data (CELLO, CLEO, BaBar, Belle) on the pion-photon TFF by means of light-cone pQCD approach in which we include the next-to-leading order correction to the valence-quark contribution and estimate the non-valence-quark contribution by a phenomenological model based on the TFF's limiting behavior at both Q20Q^2\to 0 and Q2Q^2\to\infty. At present, the pion DA is not definitely determined, it is helpful to have a pion DA model that can mimic all the suggested behaviors, especially to agree with the constraints from the pion-photon TFF in whole measured region within a consistent way. For the purpose, we adopt the conventional model for pion wavefunction/DA that has been constructed in our previous paper \cite{hw1}, whose broadness is controlled by a parameter BB. We fix the DA parameters by using the CELLO, CLEO, BABAR and Belle data within the smaller Q2Q^2 region (Q215Q^2 \leq 15 GeV2^2), where all the data are consistent with each other. And then the pion-photon TFF is extrapolated into larger Q2Q^2 region. We observe that the BABAR favors B=0.60B=0.60 which has the behavior close to the Chernyak-Zhitnitsky DA, whereas the recent Belle favors B=0.00B=0.00 which is close to the asymptotic DA. We need more accurate data at large Q2Q^2 region to determine the precise value of BB, and the definite behavior of pion DA can be concluded finally by the consistent data in the coming future.Comment: 6 pages, 5 figures. Slightly changed and references update

    Surface operator content of the A_L face models

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    A set of fixed boundary weights for both the critical dense and dilute A_L face models is constructed from the known boundary weights of the related loop model. The surface operator content and the conformal partition functions then follow from the results obtained via the Bethe equations.Comment: 12 pages, LaTeX, 2 eps figs, Elsevier style files, to appear in the Hans van Leeuwen festschrift (Physica A
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