22 research outputs found

    Iso-curvature fluctuations through axion trapping by cosmic string wakes

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    We consider wake-like density fluctuations produced by cosmic strings at the quark-hadron transition in the early universe. We show that low momentum axions which are produced through the radiation from the axionic string at an earlier stage, may get trapped inside these wakes due to delayed hadronization in these overdense regions. As the interfaces, bordering the wakes, collapse, the axions pick-up momentum from the walls and finally leave the wake regions. These axions thus can produce large scale iso-curvature fluctuations. We have calculated the detailed profile of these axionic density fluctuations and discuss its astrophysical consequences.Comment: 23 pages, 4 figures, RevTe

    Azimuthal flow of decay photons in relativistic nuclear collisions

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    An overwhelming fraction of photons from relativistic heavy ion collisions has its origin in the decay of π0\pi^0 and η\eta mesons. We calculate the azimuthal asymmetry of the decay photons for several azimuthally asymmetric pion distributions. We find that the kTk_T dependence of the elliptic flow parameterv2v_2 for the decay photons closely follows the elliptic flow parameter v2π0v_2^{\pi^0} evaluated at pTkT+δp_T \approx k_T+\delta, where δ\delta\approx 0.1 -- 0.2 GeV, for typical pion distributions measured in nucleus-nucleus collisions at relativistic energies. Similar results are obtained for photons from the 2-γ\gamma decay of η\eta mesons. Assuming that the flow of π0\pi^0 is similar to those for π+\pi^+ and π\pi^- for which independent measurements would be generally available, this ansatz can help in identifying additional sources for photons. Taken along with quark number scaling suggested by the recombination model, it may help to estimate v2v_2 of the parton distributions in terms of azimuthal asymmetry of the decay photons at large kTk_T.Comment: 6 pages, figures added, references added, with more elaborate discussion

    Effects of Phase Transition induced density fluctuations on pulsar dynamics

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    We show that density fluctuations during phase transitions in pulsar cores may have non-trivial effects on pulsar timings, and may also possibly account for glitches and anti-glitches. These density fluctuations invariably lead to non-zero off-diagonal components of the moment of inertia, leading to transient wobbling of star. Thus, accurate measurements of pulsar timing and intensity modulations (from wobbling) may be used to identify the specific pattern of density fluctuations, hence the particular phase transition, occurring inside the pulsar core. Changes in quadrupole moment from rapidly evolving density fluctuations during the transition, with very short time scales, may provide a new source for gravitational waves.Comment: 9 pages, 1 figure. arXiv admin note: substantial text overlap with arXiv:1412.427

    Strings with a confining core in a Quark-Gluon Plasma

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    We consider the intersection of N different interfaces interpolating between different ZNZ_N vacua of an SU(N) gauge theory using the Polyakov loop order parameter. Topological arguments show that at such a string-like junction, the order parameter should vanish, implying that the core of this string (i.e. the junction region of all the interfaces) is in the confining phase. Using the effective potential for the Polyakov loop proposed by Pisarski for QCD, we use numerical minimization technique and estimate the energy per unit length of the core of this string to be about 2.7 GeV/fm at a temperature about twice the critical temperature. For the parameters used, the interface tension is obtained to be about 7 GeV/fm2^2. Lattice simulation of pure gauge theories should be able to investigate properties of these strings. For QCD with quarks, it has been discussed in the literature that this ZNZ_N symmetry may still be meaningful, with quark contributions leading to explicit breaking of this ZNZ_N symmetry. With this interpretation, such {\it QGP} strings may play important role in the evolution of the quark-gluon plasma phase and in the dynamics of quark-hadron transition.Comment: 18 pages, 6 figures, RevTe

    Glitches due to (quasi) neutron-vortex scattering in the superfluid inner crust of a pulsar

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    We revisit the mechanism of vortex unpinning caused by the neutron-vortex scattering \cite{prad1} in the inner crust of a pulsar. The strain energy released by the crustquake is assumed to be absorbed in some part of the inner crust and causes pair-breaking quasi-neutron excitations from the existing free neutron superfluid in the bulk of the inner crust. The scattering of these quasi-neutrons with the vortex core normal neutrons unpins a large number of vortices from the thermally affected regions and results in pulsar glitches. We consider the geometry of a cylindrical shell of the affected pinning region to study the implications of the vortex unpinning in the context of pulsar glitches. We find that a pulsar can release about 10111013\sim 10^{11} - 10^{13} vortices by this mechanism. These numbers are equivalent to the glitch size of orders 1011109\sim 10^{-11} - 10^{-9} for Vela-like pulsars with the characteristic age τ104\tau \simeq 10^4 years. We also suggest a possibility of a vortex avalanche triggered by the movement of the unpinned vortices. A rough estimate of the glitch size caused by an avalanche shows an encouraging result.Comment: 12 pages, 5 figures, Accepted for publication in PR

    Baryon Inhomogeneity Generation in the Quark-Gluon Plasma Phase

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    We discuss the possibility of generation of baryon inhomogeneities in a quark-gluon plasma phase due to moving Z(3) interfaces. By modeling the dependence of effective mass of the quarks on the Polyakov loop order parameter, we study the reflection of quarks from collapsing Z(3) interfaces and estimate resulting baryon inhomogeneities in the context of the early universe. We argue that in the context of certain low energy scale inflationary models, it is possible that large Z(3) walls arise at the end of the reheating stage. Collapse of such walls could lead to baryon inhomogeneities which may be separated by large distances near the QCD scale. Importantly, the generation of these inhomogeneities is insensitive to the order, or even the existence, of the quark-hadron phase transition. We also briefly discuss the possibility of formation of quark nuggets in this model, as well as baryon inhomogeneity generation in relativistic heavy-ion collisions.Comment: 11 pages, 2 figures, revtex4, more detailed discussion added about formation and evolution of Z(3)domain walls in the univers