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Kawai S.,Sungkyunkwan University | Nakayama Y.,California Institute of Technology | Nakayama Y.,Kavli Institute for the Physics and Mathematics of the Universe
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

Assuming gauge/gravity correspondence we study reheating of the Universe using its holographic dual. Inflaton decay and thermalisation of the decay products correspond to collapse of a spherical shell and formation of a blackhole in the dual anti-de Sitter (AdS) spacetime. The reheating temperature is computed as the Hawking temperature of the developed blackhole probed by a dynamical boundary, and is determined by the inflaton energy density and the AdS radius, with corrections from the dynamics of the shell collapse. For given initial energy density of the inflaton field the holographic model typically gives lower reheating temperature than the instant reheating scenario, while it is shown to be safely within phenomenological bounds. © 2016 The Author(s) Source

Kawai S.,Sungkyunkwan University | Nakayama Y.,California Institute of Technology | Nakayama Y.,Kavli Institute for the Physics and Mathematics of the Universe
Journal of High Energy Physics

In holographic models of cosmology based on the (A)dS/CFT correspondence, conformal symmetry is implicit in the dual description of the Universe. Generically, however, one cannot expect the (broken) conformal invariance in the cosmic fluctuations as only the scale invariance is manifest in experiments. Also, in order for the prediction of the holographic models to make sense, the conformal symmetry needs to be broken as the scalar mode of the metric fluctuations becomes pure gauge in the conformal limit. We discuss the improvement ambiguity of the energy-momentum tensor in this context and construct a holographic model of the Universe that preserves the scale invariance but not necessarily the full conformal invariance. Our sample computation using a weakly coupled dual field theory shows that the orthogonal type of non-Gaussianity is present over and above the equilateral type. The improvement ambiguity corresponds to the choice of the energy momentum tensor that will couple to our particle physics sector after inflation. Our results show that the holographic prediction of the cosmological parameters crucially depends on such a choice. © 2014 The Author(s). Source

Isaev A.P.,Moscow State University | Kirillov A.N.,Kyoto University | Kirillov A.N.,Kavli Institute for the Physics and Mathematics of the Universe | Kirillov A.N.,National Research University Higher School of Economics | And 2 more authors.
Journal of Physics A: Mathematical and Theoretical

Commutative sets of Jucys-Murphy elements for affine braid groups of A(1) , B(1), C(1), D(1) types were defined. Construction of R-matrix representations of the affine braid group of type C(1) and its distinguished commutative subgroup generated by the C(1)-type Jucys-Murphy elements are given. We describe a general method to produce flat connections for the two-boundary quantum Knizhnik-Zamolodchikov equations as necessary conditions for Sklyanin's type transfer matrix associated with the two-boundary multicomponent Zamolodchikov algebra to be invariant under the action of the C(1)-type Jucys-Murphy elements. We specify our general construction to the case of the Birman-Murakami-Wenzl algebras (BMW algebras for short). As an application we suggest a baxterization of the Dunkl-Cherednik elements Y's in the double affine Hecke algebra of type A. © 2016 IOP Publishing Ltd Printed in the UK. Source

Ju W.,Princeton University | Greene J.E.,Princeton University | Rafikov R.R.,Princeton University | Bickerton S.J.,Kavli Institute for the Physics and Mathematics of the Universe | Badenes C.,University of Pittsburgh
Astrophysical Journal

Supermassive black hole (SMBH) binaries are expected in a ΛCDM cosmology given that most (if not all) massive galaxies contain a massive black hole (BH) at their center. So far, however, direct evidence for such binaries has been elusive. We use cross-correlation to search for temporal velocity shifts in the Mg II broad emission lines of 0.36 < z < 2 quasars with multiple observations in the Sloan Digital Sky Survey. For ∼109 M ⊙BHs in SMBH binaries, we are sensitive to velocity drifts for binary separations of ∼0.1 pc with orbital periods of ∼100 yr. We find seven candidate sub-parsec-scale binaries with velocity shifts >3.4σ ∼ 280 km s-1, where σ is our systematic error. Comparing the detectability of SMBH binaries with the number of candidates (N ≤ 7), we can rule out that most 109 M ⊙ BHs exist in ∼0.03-0.2 pc scale binaries, in a scenario where binaries stall at sub-parsec scales for a Hubble time. We further constrain that ≤16% (one-third) of quasars host SMBH binaries after considering gas-assisted sub-parsec evolution of SMBH binaries, although this result is very sensitive to the assumed size of the broad line region. We estimate the detectability of SMBH binaries with ongoing or next-generation surveys (e.g., Baryon Oscillation Spectroscopic Survey, Subaru Prime Focus Spectrograph), taking into account the evolution of the sub-parsec binary in circumbinary gas disks. These future observations will provide longer time baselines for searches similar to ours and may in turn constrain the evolutionary scenarios of SMBH binaries. © 2013. The American Astronomical Society. All rights reserved. Source

Ishikawa K.-I.,Hiroshima University | Iwasaki Y.,University of Tsukuba | Nakayama Yu.,Kavli Institute for the Physics and Mathematics of the Universe | Yoshie T.,University of Tsukuba
Physical Review D - Particles, Fields, Gravitation and Cosmology

We investigate SU(3) gauge theories in four dimensions with Nf fundamental fermions on a lattice using the Wilson fermion. Clarifying the vacuum structure in terms of Polyakov loops in spatial directions and properties of temporal propagators using a new method that we call "local analysis," we conjecture that the "conformal region" exists together with the confining region and the deconfining region in the phase structure parametrized by β and K, both in the cases of the large Nf QCD within the conformal window (referred as conformal QCD) with an IR cutoff and small Nf QCD at T/Tc>1 with Tc being the chiral transition temperature (referred to as high-temperature QCD). Our numerical simulation on a lattice of the size 163×64 shows the following evidence of the conjecture. In the conformal region, we find that the vacuum is the nontrivial Z(3) twisted vacuum modified by nonperturbative effects and that temporal propagators of mesons behave at large t as a power-law-corrected Yukawa-type decaying form. The transition from the conformal region to the deconfining region or the confining region is a sharp transition between different vacua, and therefore, it suggests a first-order transition both in conformal QCD and high-temperature QCD. To confirm the conjecture and distinguish it from the possibility of crossover phenomena, we need to take the continuum/thermodynamic limit, which we do not attempt in this work. Within our fixed-lattice simulation, we find that there is a precise correspondence between conformal QCD and high-temperature QCD in the temporal propagators under the change of the parameters Nf and T/Tc, respectively: one boundary is close to meson states, and the other is close to free quark states. In particular, conformal QCD with Nf=7 corresponds to high-temperature QCD with Nf=2 at T∼2Tc, both of which are in close relation to a meson unparticle model. From this, we estimate the anomalous mass dimension γ*=1.2(1) for Nf=7. We also show that the asymptotic state in the limit T/Tc→is a free quark state in the Z(3) twisted vacuum. The approach to a free quark state is very slow; even at T/Tc∼105, the state is affected by nonperturbative effects. This is possibly connected with the slow approach of the free energy to the Stefan-Boltzmann ideal gas limit. © 2014 American Physical Society. Source

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