Viscous generalized Chaplygin gas as a unified dark fluid: including perturbation of bulk viscosity

In this paper, we continue our previous work of studying viscous generalized Chaplygin gas as a unified dark fluid but the bulk viscosity perturbations. By using the currently available cosmic observational data from SNLS3, BAO, HST, and recently released Planck, we obtain a constraint on the bulk viscosity coefficient: <math><mrow><msub><mi mathvariant="italic">ζ</mi><mn>0</mn></msub><mo>=</mo><mn>0</mn><mo>.</mo><msubsup><mn>0000138</mn><mrow><mo>-</mo><mn>0.0000105</mn><mo>-</mo><mn>0.0000138</mn><mo>-</mo><mn>0.0000138</mn></mrow><mrow><mo>+</mo><mn>0.00000614</mn><mo>+</mo><mn>0.0000145</mn><mo>+</mo><mn>0.0000212</mn></mrow></msubsup></mrow></math> in <math><mrow><mn>1</mn><mo>,</mo><mn>2</mn><mo>,</mo><mn>3</mn><mi mathvariant="italic">σ</mi></mrow></math> regions, respectively, via the Markov Chain Monte Carlo method. The result shows that when considering perturbations of the bulk viscosity, the current cosmic observations favor a smaller bulk viscosity coefficient

Baryogenesis from the inflaton field

In this letter we show that the inflaton can generate the cosmological baryon asymmetry. We take the inflaton to be a complex scalar field with a weakly broken global symmetry and develop a new variant on the Affleck–Dine mechanism. The inflationary phase is driven by a quadratic potential whose amplitude of B-modes is in agreement with BICEP2 data. We show that a conserved particle number is produced in the latter stage of inflation, which can later decay to baryons. We present promising embeddings in particle physics, including the use of high dimension operators for decay or using a colored inflaton. We also point out observational consequences, including a prediction of isocurvature fluctuations, whose amplitude is just below current limits, and a possible large scale dipole

Probing shadowed nuclear sea with massive gauge bosons in the future heavy-ion collisions

The production of the massive bosons Z0 and W± could provide an excellent tool to study cold nuclear matter effects and the modifications of nuclear parton distribution functions (nPDFs) relative to the parton distribution functions (PDFs) of a free proton in high-energy nuclear reactions at the LHC as well as in heavy-ion collisions (HIC) with much higher center-of-mass energies available in the future colliders. In this paper we calculate the rapidity and transverse momentum distributions of the vector boson and their nuclear modification factors in p + Pb collisions at sNN=63  TeV and in Pb + Pb collisions at sNN=39  TeV in the framework of perturbative QCD by utilizing three parametrization sets of nPDFs: EPS09, DSSZ, and nCTEQ. It is found that in heavy-ion collisions at such high colliding energies, both the rapidity distribution and the transverse momentum spectrum of vector bosons are considerably suppressed in wide kinematic regions with respect to p + p reactions due to large nuclear shadowing effect. We demonstrate that the massive vector boson production processes with sea quarks in the initial state may give more contributions than those with valence quarks in the initial state; therefore in future heavy-ion collisions the isospin effect is less pronounced and the charge asymmetry of the W boson will be reduced significantly as compared to that at the LHC. A large difference between results with nCTEQ and results with EPS09 and DSSZ is observed in nuclear modifications of both rapidity and pT distributions of Z0 and W in the future HIC

Charged charmonium-like Z+(4430) from rescattering in conventional B decays

In a previous paper we suggested an explanation for the peak designated as Z(4430)+ in the ψ′π+ mass spectrum, observed by Belle in B¯→ψ′π+K decays, as an effect of D¯⁎0D+→ψ′π+ rescattering in the decays B¯→Ds′−D , where the Ds′− is an as-yet unobserved radial excitation of the pseudoscalar ground state Ds− -meson. In this paper, we demonstrate that this hypothesis provides an explanation of the double Z+ -like peaking structures, which were studied by LHCb with much higher statistics. While according to our hypothesis, the origin of the peaking structures is due to the kinematical reflection of conventional resonances in the unobserved intermediate state, the amplitude of the Z(4430)+ peak carries a Breit–Wigner-like complex phase, arising from the intermediate Ds′− resonance. Thus, our hypothesis is entirely consistent with the recent LHCb measurement of the resonant-like amplitude behavior of the Z(4430)+ . We perform a toy fit to the LHCb data, which illustrates that our approach is also consistent with all the observed structure in the LHCb M(ψ′π+) spectrum. We suggest a critical test of our hypothesis that can be performed experimentally

Conformal higher-spin symmetries in twistor string theory

It is shown that similarly to massless superparticle, classical global symmetry of the Berkovits twistor string action is infinite-dimensional. We identify its superalgebra, whose finite-dimensional subalgebra contains psl(4|4,R) superalgebra. In quantum theory this infinite-dimensional symmetry breaks down to SL(4|4,R) one

Predictions on the transverse momentum spectra for charged particle production at LHC-energies from a two component model

Transverse momentum spectra, d2σ/(dηdpT2) , of charged hadron production in pp -collisions are considered in terms of a recently introduced two component model. The shapes of the particle distributions vary as a function of the c.m.s. energy in the collision and the measured pseudorapidity interval. As a result the pseudorapidity of a secondary hadron in the moving proton rest frame is shown to be a universal parameter describing the shape of the spectra in pp -collisions. In order to extract predictions on the double-differential cross sections d2σ/(dηdpT2) of hadron production for future LHC-measurements the different sets of available experimental data have been used in this study

Localized shocks

We study products of precursors of spatially local operators, W x n t n ⋅ ⋅ ⋅ W x 1 t 1 $${W_x}_{{}_n}(tn)\cdot \cdot \cdot {W}_{x_1}\left({t}_1\right)$$ , where W x ( t ) =  e −  iHt W x e iHt . Using chaotic spin-chain numerics and gauge/gravity duality, we show that a single precursor fills a spatial region that grows linearly in t . In a lattice system, products of such operators can be represented using tensor networks. In gauge/gravity duality, they are related to Einstein-Rosen bridges supported by localized shock waves. We find a geometrical correspondence between these two descriptions, generalizing earlier work in the spatially homogeneous case

Inflation, symmetry, and B-modes

We examine the role of using symmetry and effective field theory in inflationary model building. We describe the standard formulation of starting with an approximate shift symmetry for a scalar field, and then introducing corrections systematically in order to maintain control over the inflationary potential. We find that this leads to models in good agreement with recent data. On the other hand, there are attempts in the literature to deviate from this paradigm by envoking other symmetries and corrections. In particular: in a suite of recent papers, several authors have made the claim that standard Einstein gravity with a cosmological constant and a massless scalar carries conformal symmetry. They claim this conformal symmetry is hidden when the action is written in the Einstein frame, and so has not been fully appreciated in the literature. They further claim that such a theory carries another hidden symmetry; a global SO(1,1) symmetry. By deforming around the global SO(1,1) symmetry, they are able to produce a range of inflationary models with asymptotically flat potentials, whose flatness is claimed to be protected by these symmetries. These models tend to give rise to B-modes with small amplitude. Here we explain that standard Einstein gravity does not in fact possess conformal symmetry. Instead these authors are merely introducing a redundancy into the description, not an actual conformal symmetry. Furthermore, we explain that the only real (global) symmetry in these models is not at all hidden, but is completely manifest when expressed in the Einstein frame; it is in fact the shift symmetry of a scalar field. When analyzed systematically as an effective field theory, deformations do not generally produce asymptotically flat potentials and small B-modes as suggested in these recent papers. Instead, deforming around the shift symmetry systematically, tends to produce models of inflation with B-modes of appreciable amplitude. Such simple models typically also produce the observed red spectral index, Gaussian fluctuations, etc. In short: simple models of inflation, organized by expanding around a shift symmetry, are in excellent agreement with recent data

The condensate from torus knots

We discuss recently formulated instanton-torus knot duality in Ω-deformed 5D SQED on ℝ 4 × S 1 $${\mathrm{\mathbb{R}}}^4\times {S}^1$$ focusing at the microscopic aspects of the condensate formation in the instanton ensemble. Using the chain of dualities and geometric transitions we embed the SQED with a surface defect into the SU(2) SQCD with N f = 4 and identify the numbers ( n , m ) of the torus T n , m knot as instanton charge and electric charge. The HOMFLY torus knot invariants in the fundamental representation provide entropic factor in the condensate of the massless flavor counting the degeneracy of the instanton-W-boson web with instanton and electric numbers ( n , m ) but different spin and flavor content. Using the inverse geometrical transition we explain how our approach is related to the evaluation of the HOMFLY invariants in terms of Wilson loop in 3d CS theory. The reduction to 4D theory is briefly considered and some analogy with baryon vertex is conjectured

A simple holographic superconductor with momentum relaxation

We study a holographic superconductor model with momentum relaxation due to massless scalar fields linear to spatial coordinates( ψ I  =  βδ Ii x i ), where β is the strength of momentum relaxation. In addition to the original superconductor induced by the chemical potential( μ ) at β = 0, there exists a new type of superconductor induced by β even at μ = 0. It may imply a new ‘pairing’ mechanism of particles and antiparticles interacting with β , which may be interpreted as ‘impurity’. Two parameters μ and β compete in forming superconducting phase. As a result, the critical temperature behaves differently depending on β/μ . It decreases when β/μ is small and increases when β/μ is large, which is a novel feature compared to other models. After analysing ground states and phase diagrams for various β/μ , we study optical electric( σ ), thermoelectric( α ), and thermal( κ ¯ $$\overline{\kappa}$$ ) conductivities. When the system undergoes a phase transition from normal to a superconducting phase, 1 /ω pole appears in the imaginary part of the electric conductivity, implying infinite DC conductivity. If β/μ < 1, at small ω , a two-fluid model with an imaginary 1 /ω pole and the Drude peak works for σ , α , and κ ¯ $$\overline{\kappa}$$ , but If β/μ > 1 a non-Drude peak replaces the Drude peak. It is consistent with the coherent/incoherent metal transition in its metal phase. The Ferrell-Glover-Tinkham (FGT) sum rule is satisfied for all cases even when μ = 0