76,154 research outputs found

    Tachyon Condensation with B-field

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    We discuss classical solutions of a graviton-dilaton-B_{\mu\nu}-tachyon system. Both constant tachyon solutions, including AdS_3 solutions, and space-dependent tachyon solutions are investigated, and their possible implications to closed string tachyon condensation are argued. The stability issue of the AdS_3 solutions is also discussed.Comment: 10 pages, references adde

    The nonperturbative closed string tachyon vacuum to high level

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    We compute the action of closed bosonic string field theory at quartic order with fields up to level ten. After level four, the value of the potential at the minimum starts oscillating around a nonzero negative value, in contrast with the proposition made in [5]. We try a different truncation scheme in which the value of the potential converges faster with the level. By extrapolating these values, we are able to give a rather precise value for the depth of the potential.Comment: 24 pages. v2: typos corrected, clarified extrapolation in scheme B, and added extrapolated tachyon and dilaton vev's at the end of Section

    Axion Dark Matter and Cosmological Parameters

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    We observe that photon cooling after big bang nucleosynthesis (BBN) but before recombination can remove the conflict between the observed and theoretically predicted value of the primordial abundance of 7^7Li. Such cooling is ordinarily difficult to achieve. However, the recent realization that dark matter axions form a Bose-Einstein condensate (BEC) provides a possible mechanism, because the much colder axions may reach thermal contact with the photons. This proposal predicts a high effective number of neutrinos as measured by the cosmic microwave anisotropy spectrum.Comment: 4 pages, one figure. Version to appear in Phys. Rev. Lett., incorporating useful comments by the referees and emphasizing that photon cooling by axion BEC is a possibility, not a certaint

    Semiquantitative Infrared Analysis of Diketones and Anhydrides in a Reaction Mixture

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    The ozonolysis of a hydroxymethylene ketone yields a mixture of diketone and anhydride. Treatment of hydroxymethylene camphor with ozone affords, in addition to the expected camphor quinone, a surprisingly large amount of camphoric anhydride (56%) via Baeyer-Villager reaction. Use of infrared absorption to analyze the relative amounts of camphor quinone and camphoric anhydride in a reaction mixture was studied by comparing peak heights of their carbonyl stretching bands

    Off-Diagonal Long-Range Order: Meissner Effect and Flux Quantization

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    There has been a proof by Sewell that the hypothesis of off-diagonal long-range order in the reduced density matrix ρ2\rho _2 implies the Meissner effect. We present in this note an elementary and straightforward proof that not only the Meissner effect but also the property of magnetic flux quantization follows from the hypothesis. It is explicitly shown that the two phenomena are closely related, and phase coherence is the origin for both.Comment: 11 pages, Latex fil

    Identities in the Superintegrable Chiral Potts Model

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    We present proofs for a number of identities that are needed to study the superintegrable chiral Potts model in the Q0Q\ne0 sector.Comment: LaTeX 2E document, using iopart.cls with iopams packages. 11 pages, uses eufb10 and eurm10 fonts. Typeset twice! vs2: Two equations added. vs3: Introduction adde

    Possibly New Charmed Baryon States from Bˉ0ppˉD0\bar B^0\to p\bar p D^{0} Decay

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    We examine the invariant mass spectrum of D0pD^{0}p in Bˉ0ppˉD0\bar B^0\to p\bar p D^{0} decay measured by BABAR and find that through the 2-step processes of Bˉ0Bc+(D0p)pˉ\bar B^0\to {\bf B_c^+}(\to D^{0} p)\bar p, where Bc{\bf B_c} denotes a charmed baryon state, some of the peaks can be identified with the established Σc(2800)+\Sigma_c(2800)^+, Λc(2880)+\Lambda_c(2880)^+ and Λc(2940)+\Lambda_c(2940)^+. Moreover, in order to account for the measured spectrum, it is necessary to introduce a new charmed baryon resonance with (m,Γ)=(3212±20,167±34)(m,\,\Gamma)=(3212\pm 20,\,167\pm 34) MeV.Comment: 8 pages, 1 figure, title changed and discussions updated, version accepted for publication in Phys. Rev.

    Multi-quark components in baryons

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    A brief review on some recent progresses in our understanding of multi-quark components in baryons is presented. The multi-quark components in baryons seem to be mainly in colored quark cluster configurations rather than in ``meson cloud'' configurations or in the form of a sea of quark-antiquark pairs. The colored quark cluster multi-quark picture gives a natural explanation of empirical indications for a positive strangeness magnetic moment μs\mu_s of the proton and the longstanding mass-reverse problem of S11(1535) and P11(1440)Nresonances.AmodelpredictionfortheP11(1440) N* resonances. A model-prediction for the \mu_s$ of the proton is given.Comment: Contribution to the International Conference on QCD and Hadronic Physics, June 16-20, 2005, Beijin

    Instability and Periodic Deformation in Bilayer Membranes Induced by Freezing

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    The instability and periodic deformation of bilayer membranes during freezing processes are studied as a function of the difference of the shape energy between the high and the low temperature membrane states. It is shown that there exists a threshold stability condition, bellow which a planar configuration will be deformed. Among the deformed shapes, the periodic curved square textures are shown being one kind of the solutions of the associated shape equation. In consistency with recent expe rimental observations, the optimal ratio of period and amplitude for such a texture is found to be approximately equal to (2)^{1/2}\pi.Comment: 8 pages in Latex form, 1 Postscript figure. To be appear in Mod. Phys. Lett. B. 199
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