Fri·Jul 22, 2016Friday·July 22, 2016

1. 01*

   Reconstruction of Monte Carlo replicas from Hessian parton distributions

   Tie-Jiun Hou🇺🇸 · Jun Gao🇺🇸 · Joey Huston🇺🇸 · Pavel Nadolsky🇺🇸 · Carl Schmidt🇺🇸 · Daniel Stump🇺🇸 · Bo-Ting Wang🇺🇸 · Ke-Ping Xie🇺🇸 · Sayipjamal Dulat🇨🇳 · Jon Pumplin🇺🇸 · C.-P. Yuan🇺🇸

   We explore connections between two common methods for quantifying the uncertainty in parton distribution functions (PDFs), based on the Hessian error matrix and Monte-Carlo sampling. CT14 parton distributions in the Hessian representation are converted into Monte-Carlo replicas by a numerical method that reproduces important properties of CT14 Hessian PDFs: the asymmetry of CT14 uncertainties and positivity of individual parton distributions. The ensembles of CT14 Monte-Carlo replicas constructed this way at NNLO and NLO are suitable for various collider applications, such as cross section reweighting. Master formulas for computation of asymmetric standard deviations in the Monte-Carlo representation are derived. A correction is proposed to address a bias in asymmetric uncertainties introduced by the Taylor series approximation. A numerical program is made available for conversion of Hessian PDFs into Monte-Carlo replicas according to normal, log-normal, and Watt-Thorne sampling procedures.

   hep-phJHEP(2017)·70 citations
2. 02*

   Exploring Peaks and Valleys in the Diphoton Spectrum

   Nathaniel Craig🇺🇸 · Sophie Renner🇬🇧 · Dave Sutherland🇺🇸

   We investigate the effects of resonance-continuum interference on the diphoton spectrum in the presence of a new spin-0 or spin-2 state produced via gluons or quarks and decaying to pairs of photons. Interference effects can significantly influence the extraction of resonance masses and widths from the diphoton spectrum, particularly in the case of a spin-2 resonance produced via quarks. We illustrate these effects via a binned likelihood analysis of LHC diphoton data at both 8 and 13 TeV.

   hep-phhep-exPRD(2016)·6 citations
3. 03*

   Searching for axion-like particles with ultra-peripheral heavy-ion collisions

   Simon Knapen🇺🇸 · Tongyan Lin🇺🇸 · Hou Keong Lou🇺🇸 · Tom Melia🇺🇸

   We show that ultra-peripheral heavy-ion collisions at the LHC can be used to search for axion-like particles with mass below 100 GeV. The $Z^4$ enhanced photon-photon luminosity from the ions provides a large exclusive production rate, with a signature of a resonant pair of back-to-back photons and no other activity in the detector. In addition, we present both new and updated limits from recasting multi-photon searches at LEP II and the LHC, which are more stringent than those currently in the literature for the mass range 100 MeV to 100 GeV.

   hep-phhep-exPRL(2017)·334 citations
4. 04*

   The vacuum structure of the Higgs complex singlet-doublet model

   P.M. Ferreira🇵🇹

   The complex singlet-doublet model is a popular theory to account for dark matter and electroweak baryogenesis, wherein the Standard Model particle content is supplemented by a complex scalar gauge singlet, with certain discrete symmetries imposed. The scalar potential which results thereof can have seven different types of minima at tree-level, which may coexist for specific choices of parameters. There is therefore the possibility that a given minimum is not global but rather a local one, and may tunnel to a deeper extremum, thus causing vacuum instability. This rich vacuum structure is explained and discussed in detail.

   hep-phPRD(2016)·22 citations
5. 05*

   A holographic model for the baryon octet

   Zhen Fang🇨🇳

   By adopting the nonlinear realization of chiral symmetry, a holographic model for the baryon octet is proposed. The mass spectra of the baryon octet and their low-lying excited states are calculated, which show good consistency with experiments. The couplings of pion to nucleons are derived in two gauges and are shown to be equivalent with each other. It also shows that only derivative couplings of pion to nucleons appear in this holographic model. The coupling constant is then calculated.

   hep-phPRD(2016)·10 citations
6. 06*

   Development of a low-energy, high-brightness ${\mu }^{+}$ beam line

   A. Eggenberger🇨🇭 · I. Belosevic🇨🇭 · G. Wichmann🇨🇭

   We are developing a beam line which compresses the phase space of a standard surface ${\mu }^{+}$ beam by 10 orders of magnitude with an efficiency of $10^{-3}$. Phase space compression occurs in a He gas target and consists of three consecutive stages: Transverse (perpendicular to the beam axis) compression, longitudinal compression and re-extraction into vacuum. Transverse compression was observed for the first time and longitudinal compression has been measured to occur within 2.5 $\mu$s with high efficiency.

   hep-phphysics.acc-ph4 citations
7. 07*

   Phenomenology of dark matter in chiral U(1)${}_X$ dark sector

   P. Ko🇰🇷 · Takaaki Nomura🇰🇷

   We consider dark matter physics in a model for the dark sector with extra dark U(1)${}_X$ gauge symmetry. The dark sector is composed of exotic fermions that are charged under both dark U(1)${}_X$ and the standard model SU(3)${}_C\times$U(1)${}_Y$ gauge groups, as well as standard model singlet complex scalars $\Phi$ and $X$ with nonzero U(1)${}_X$ charge. In this model, there are two dark matter candidates$-$a scalar and a fermion$-$both of which are stabilized by accidental $Z_2$ symmetry. Their thermal relic density, and direct and indirect detection constraints are discussed in detail and we search for the parameter space of the model accommodating dark matter observations. We also discuss constraints from diphoton resonance searches associated with the scalar field which breaks the dark U(1)${}_X$, in a way consistent with dark matter physics. In addition, implications for collider physics are discussed, focusing on the production cross section of the scalar boson.

   hep-phhep-exPRD(2016)·11 citations
8. 08*

   Modified top quark condensation model with the extra heavy fermion, the $125$ GeV Pseudo - Goldstone boson, and the additional heavy scalar bosons

   Z.V.Khaidukov🇷🇺 · M.A.Zubkov

   We discuss the modified top quark condensation model proposed in \cite{VZ2015}. This construction was inspired by the top - seesaw scenario, in which the extra heavy fermion $\chi$ is added that may be paired with the top quark. Besides, this model incorporates the ideas of the Little Higgs scenario, in which the $125$ GeV scalar particle appears as a Pseudo - Goldstone boson. This model admits (in addition to the $125$ GeV scalar boson $H$) the heavier scalar excitation $H^{\prime }$. We consider the region of parameters, where its mass is $M_{H^{\prime }}\sim 1$ TeV, the width of $H^{\prime }$ is ${\Gamma }_{H^{\prime }}\sim 0.3M_{H^{\prime }}$, while the mass of the heavy fermion is $m_{\chi }\sim 1$ TeV. We find that in this model the value of the cross - section ${\sigma }_{pp\to H^{\prime }+X\to \gamma +\gamma +X}$ for $\sqrt{s}=13$ TeV is essentially smaller than the present experimental upper bound. Besides, we find, that for the chosen values of parameters there should exist the CP - even scalar boson with mass $\approx 2m_{\chi }$ and very small width. In addition, the model predicts the existence of the extra neutral CP even scalar boson and the charged scalar boson with masses of the order of $1$ TeV.

   hep-phInt.J.Mod.Phys.A(2017)·2 citations
9. 09*

   Solution of QCD$\otimes$QED coupled DGLAP equations at NLO

   S. Zarrin🇮🇷 · G.R. Boroun🇮🇷

   In this work, we present an analytical solution for QCD$\otimes$QED coupled Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations at the leading order (LO) accuracy in QED and next-to-leading order (NLO) accuracy in perturbative QCD using double Laplace transform. This technique is applied to obtain the singlet, gluon and photon distribution functions and also the proton structure function. We also obtain contribution of photon in proton at LO and NLO at high energy and successfully compare the proton structure function with HERA data \cite{12} and APFEL results \cite{7}. Some comparisons also have been done for the singlet and gluon distribution functions with the MSTW results\cite{9}. In addition, the contribution of photon distribution function inside the proton has been compared with results of MRST \cite{11} and with the contribution of sea quark distribution functions which obtained by MSTW \cite{9} and CTEQ6M \cite{14}.

   hep-phNPB(2017)·17 citations
10. 10*

    N(N)LO event files: applications and prospects

    Gudrun Heinrich🇩🇪 · Mark Johnson🇬🇧 · Daniel Maitre🇬🇧

    In this contribution we comment on the use of NLO n-Tuples and consider their extension to NNLO. As an application of n-Tuples we present preliminary results of a strong coupling extraction from a measurement of the production of Z + 2, 3, 4 jets at the LHC at 7 TeV.

    hep-phPoS(2016)·14 citations
11. 11*

    The muon magnetic moment in the 2HDM: complete two-loop result

    Adriano Cherchiglia🇩🇪 · Patrick Kneschke🇩🇪 · Dominik Stöckinger🇩🇪 · Hyejung Stöckinger-Kim🇩🇪

    We study the $\text{2HDM}$ contribution to the muon anomalous magnetic moment $a_{\mu }$ and present the complete two-loop result, particularly for the bosonic contribution. We focus on the Aligned $\text{2HDM}$, which has general Yukawa couplings and contains the type I, II, X, Y models as special cases. The result is expressed with physical parameters: three Higgs boson masses, Yukawa couplings, two mixing angles, and one quartic potential parameter. We show that the result can be split into several parts, each of which has a simple parameter dependence, and we document their general behavior. Taking into account constraints on parameters, we find that the full $\text{2HDM}$ contribution to $a_{\mu }$ can accommodate the current experimental value, and the complete two-loop bosonic contribution can amount to $(2\cdots 4)\times 10^{-10}$, more than the future experimental uncertainty.

    hep-phJHEP(2017)·84 citations
12. 12*

    Positivity and unitarity constraints on dipole gluon distributions

    Robi Peschanski🇫🇷

    In the high-energy domain, gluon transverse-momentum dependent distributions in nuclei obey constraints coming from positivity and unitarity of the colorless QCD dipole distributions through Fourier-Bessel transformations. Using mathematical properties of Fourier-positive functions, we investigate the nature of these constraints which apply to dipole model building and formulation

    hep-phActa Phys.Polon.B(2016)·0 citations
13. 13*

    Classical Nonminimal Lagrangians and Kinematic Tests of Special Relativity

    M. Schreck🇧🇷

    This article gives a brief summary on recently obtained classical lagrangians for the nonminimal fermion sector of the Standard-Model Extension (SME). Such lagrangians are adequate descriptions of classical particles that are subject to a Lorentz-violating background field based on the SME. Explicitly, lagrangians were obtained for the leading nonminimal contributions of the m, a, c, e, and f coefficients. These results were then used to interpret classical, kinematic tests of Special Relativity in the framework of the nonminimal SME. This led to new constraints on certain nonminimal controlling coefficients. Although the experiments were very sophisticated in the era when they were carried out, their sensitivities for detecting Lorentz violation were still far away from the Planck scale. Obtaining the novel constraints can be considered as a proof-of-principle demonstrating the applicability of the classical lagrangians computed.

    hep-ph0 citations
14. 14*

    $B_s\pi$--$B\bar{K}$ interactions in finite volume and the $X(5568)$

    Jun-Xu Lu🇨🇳 · Xiu-Lei Ren🇨🇳 · Li-Sheng Geng🇨🇳

    The recent observation of $X(5568)$ by the D0 Collaboration has aroused a lot of interest both theoretically and experimentally. In the present work, we first point out that $X(5568)$ and $D_{s0}^{\ast }(2317)$ cannot simultaneously be of molecular nature, from the perspective of heavy-quark symmetry and chiral symmetry, based on a previous study of the lattice QCD scattering lengths of $DK$ and its coupled channels. Then we compute the discrete energy levels of the $B_s\pi$ and $B\bar{K}$ system in finite volume using unitary chiral perturbation theory. The comparison with the latest lattice QCD simulation, which disfavors the existence of $X(5568)$, supports our picture where the $B_s\pi$ and $B\bar{K}$ interactions are weak and $X(5568)$ cannot be a $B_s\pi$ and $B\bar{K}$ molecular state. In addition, we show that the extended Weinberg compositeness condition also indicates that $X(5568)$ cannot be a molecular state made from $B_s\pi$ and $B\bar{K}$ interactions.

    hep-phhep-latEPJC(2017)·31 citations
15. 15*

    Lepton number violation in 331 models

    Renato M. Fonseca🇪🇸 · Martin Hirsch🇪🇸

    Different models based on the extended $SU(3{)}_C\times SU(3{)}_L\times U(1{)}_X$ (331) gauge group have been proposed over the past four decades. Yet, despite being an active research topic, the status of lepton number in 331 models has not been fully addressed in the literature, and furthermore many of the original proposals can not explain the observed neutrino masses. In this paper we review the basic features of various 331 models, focusing on potential sources of lepton number violation. We then describe different modifications which can be made to the original models in order to accommodate neutrino (and charged lepton) masses.

    hep-phPRD(2016)·40 citations
16. 16*

    QCD radiative corrections for $h\to b\bar{b}$ in the Standard Model Dimension-6 EFT

    Rhorry Gauld🇬🇧 · Benjamin D. Pecjak🇬🇧 · Darren J. Scott🇬🇧

    We calculate the $\mathcal{O}({\alpha }_s)$ QCD corrections to the inclusive $h\to b\bar{b}$ decay rate in the dimension-6 Standard Model Effective Field Theory (SMEFT). The QCD corrections multiplying the dimension-6 Wilson coefficients which alter the $hb\bar{b}$-vertex at tree-level are proportional to the Standard Model (SM) ones, so next-to-leading order results can be obtained through a simple rescaling of the tree-level decay rate. On the other hand, contributions from the operators $Q_{bG}$ and $Q_{HG}$, which alter the $gb\bar{b}$-vertex and introduce a $hgg$-vertex respectively, enter at $\mathcal{O}({\alpha }_s)$ and induce sizeable corrections which are unrelated to the SM ones and cannot be anticipated through a renormalisation-group analysis. We present compact analytic results for these contributions, which we recommend to be included in future phenomenological studies.

    hep-phPRD(2016)·53 citations
17. 17*

    Little Higgs Dark Matter after PandaX-II/LUX 2016 and LHC Run-1

    Lei Wu🇦🇺 · Bingfang Yang🇨🇳 · Mengchao Zhang🇨🇳

    In the Littlest Higgs model with $T$ parity (LHT), the $T$-odd heavy photon ($A_H$) is weakly interacting and can play the role of dark matter. We investigate the lower limit on the mass of $A_H$ dark matter under the constraints from Higgs data, EWPOs, $R_b$, Planck 2015 dark matter relic abundance, PandaX-II/LUX 2016 direct detections and LHC-8 TeV monojet results. We find that (1) Higgs data, EWPOs and $R_b$ can exclude the mass of $A_H$ up to 99 GeV. To produce the correct dark matter relic abundance, $A_H$ has to co-annihilate with $T$-odd quarks ($q_H$) or leptons (${\ell }_H$); (2) the LUX (PandaX-II) 2016 data can further exclude $m_{A_H}<380(270)$ GeV for ${\ell }_H$-$A_H$ co-annihilation and $m_{A_H}<350(240)$ GeV for $q_H-A_H$ co-annihilation; (3) LHC-8 TeV monojet result can give a strong lower limit, $m_{A_H}>540$ GeV, for $q_H$-$A_H$ co-annihilation; (4) future XENON1T (2017) experiment can fully cover the parameter space of ${\ell }_H$-$A_H$ co-annihilation and will push the lower limit of $m_{A_H}$ up to about 640 GeV for $q_H$-$A_H$ co-annihilation.

    hep-phastro-ph.COhep-exJHEP(2016)·9 citations
18. 18*

    Fully Differential Higgs Pair Production in Association With a $W$ Boson at Next-to-Next-to-Leading Order in QCD

    Hai Tao Li🇦🇺 · Jian Wang🇩🇪

    To clarify the electroweak symmetry breaking mechanism, we need to probe the Higgs self-couplings, which can be measured in Higgs pair productions. The associated production with a vector boson is special due to a clear tag in the final state. We perform a fully differential next-to-next-to-leading-order calculation of the Higgs pair production in association with a $W$ boson at hadron colliders, and present numerical results at the 14 TeV LHC and a future 100 TeV hadron collider.

    hep-phhep-exPLB(2017)·29 citations
19. 19*

    SUSY-QCD corrections for the direct detection of neutralino dark matter and correlations with the relic density

    Michael Klasen🇩🇪 · Karol Kovarik🇩🇪 · Patrick Steppeler🇩🇪

    In this paper, we perform a full next-to-leading order (NLO) QCD calculation of neutralino scattering on protons or neutrons in the MSSM. We match the results of the NLO QCD calculation to the scalar and axial-vector operators in the effective field theory approach. These govern the spin-independent and spin-dependent detection rates, respectively. The calculations have been performed for general bino, wino and higgsino decompositions of neutralino dark matter and required a novel tensor reduction method of loop integrals with vanishing relative velocities and Gram determinants. Numerically, the NLO QCD effects are shown to be of at least of similar size and sometimes larger than the currently estimated nuclear uncertainties. We also demonstrate the interplay of the direct detection rate with the relic density when consistently analyzed with the program $DM@NLO$.

    hep-phastro-ph.COPRD(2016)·29 citations
20. 20*

    Positronium and Muonium 1S-2S Laser Spectroscopy as a Probe for the Standard-Model Extension

    P. Crivelli🇨🇭 · G. Wichmann🇨🇭

    We present the status and the prospects of the ongoing efforts to improve the measurements of the 1S-2S transition in positronium and muonium. These purely leptonic systems represent ideal objects to test bound-state QED to high precision and the Standard-Model Extension.

    hep-phphysics.atom-ph8 citations
21. 21*

    Galactic cosmic-ray propagation in the light of AMS-02: I. Analysis of protons, helium, and antiprotons

    Michael Korsmeier🇩🇪 · Alessandro Cuoco (RWTH Aachen)🇩🇪

    We present novel constraints on cosmic-ray propagation in the Galaxy using the recent precise measurements of proton and helium spectra from AMS-02, together with preliminary AMS-02 data on the antiproton over proton ratio. To explore efficiently the large (up to eleven-dimensional) parameter space we employ the nested-sampling algorithm as implemented in the \textsc{MultiNest} package, interfaced with the \textsc{Galprop} code to compute the model-predicted spectra. We use VOYAGER proton and helium data, sampling the local inter-stellar spectra, to constrain the solar modulation potential. We find that the turbulence of the Galactic magnetic field is well constrained, i.e., $\delta =0.30_{-0.02}^{+0.03}(stat{)}_{-0.04}^{+0.10}(sys)$, with uncertainties dominated by systematic effects. Systematic uncertainties are determined checking the robustness of the results to the minimum rigidity cut used to fit the data (from 1 GV to 5 GV), to the propagation scenario (convection vs no-convection), and to the uncertainties in the knowledge of the antiproton production cross section. Convection and reaccelaration are found to be degenerate and not well-constrained singularly when using data above 5 GV. Using data above 1 GV reacceleration is required, $v_{\mathrm{A}}=25\pm 2$km/s, although this value might be significantly affected by the low energy systematic uncertainty in the solar modulation. In a forthcoming companion paper, we investigate the constraints imposed by AMS-02 measurements on lithium, boron, and carbon.

    ↳ astro-ph.HEhep-phPRD(2016)·78 citations
22. 22*

    Combined search for Lorentz violation in short-range gravity

    Cheng-Gang Shao🇨🇳 · Yu-Jie Tan🇨🇳 · Wen-Hai Tan🇨🇳 · Shan-Qing Yang🇨🇳 · Jun Luo🇨🇳 · Michael Edmund Tobar🇦🇺 · Quentin G. Bailey🇺🇸 · J.C. Long🇺🇸 · E. Weisman🇺🇸 · Rui Xu🇺🇸 · Alan Kostelecky🇺🇸

    Short-range experiments testing the gravitational inverse-square law at the submillimeter scale offer uniquely sensitive probes of Lorentz invariance. A combined analysis of results from the short-range gravity experiments HUST-2015, HUST-2011, IU-2012, and IU-2002 permits the first independent measurements of the 14 nonrelativistic coefficients for Lorentz violation in the pure-gravity sector at the level of $10^{-9}$ m${}^2$, improving by an order of magnitude the sensitivity to numerous types of Lorentz violation involving quadratic curvature derivatives and curvature couplings.

    ↳ gr-qchep-exhep-phPRL(2016)·80 citations
23. 23*

    A Monodromy from London

    Nemanja Kaloper🇺🇸 · Albion Lawrence🇺🇸

    We focus on the massive gauge theory formulation of axion monodromy inflation. We argue that a gauge symmetry hidden in these models is the key protection mechanism from dangerous corrections from both field theory and gravitational dynamics. The effective theory of large field inflation is a dual to a massive U(1) 4-form gauge theory, which is similar to a massive gauge theory description of superconductivity. The gauge theory explicitly realizes the old Julia-Toulouse proposal for a low energy description of a gauge theory in a defect condensate. While we work mostly with the example of quadratic axion potential induced by flux monodromy, we discuss how other types of potentials can arise from inclusion of gauge invariant corrections to the theory.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2017)·53 citations
24. 24*

    Fate of the conformal fixed point with twelve massless fermions and SU(3) gauge group

    Zoltan Fodor (University of Wuppertal)🇩🇪 · Kieran Holland (University of the Pacific)🇺🇸 · Julius Kuti (U.C. San Diego)🇺🇸 · Santanu Mondal (Eotvos University)🇭🇺 · Daniel Nogradi (Eotvos University)🇭🇺 · Chik Him Wong (University of Wuppertal)🇩🇪

    We report new results on the conformal properties of an important strongly coupled gauge theory, a building block of composite Higgs models beyond the Standard Model. With twelve massless fermions in the fundamental representation of the SU(3) color gauge group, an infrared fixed point of the $\beta$-function was recently reported in the theory (Cheng:2014jba) with uncertainty in the location of the critical gauge coupling inside the narrow $[6.0<g_{\ast }^2<6.4]$ interval and widely accepted since as the strongest evidence for a conformal fixed point and scale invariance in the theory with model-building implications. Using the exact same renormalization scheme as the previous study, we show that no fixed point of the $\beta$-function exists in the reported interval. Our findings eliminate the only seemingly credible evidence for conformal fixed point and scale invariance in the $N_f=12$ model whose infrared properties remain unresolved. The implications of the recently completed 5-loop QCD beta function for arbitrary flavor number are discussed with respect to our work.

    ↳ hep-lathep-phPRD(2016)·60 citations
25. 25*

    Six-dimensional regularization of chiral gauge theories

    Hidenori Fukaya🇯🇵 · Tetsuya Onogi🇯🇵 · Shota Yamamoto🇯🇵 · Ryo Yamamura🇯🇵

    We propose a regularization of four dimensional chiral gauge theories using six-dimensional Dirac fermions. In our formulation, we consider two different mass terms having domain-wall profiles in the fifth and the sixth directions, respectively. A Weyl fermion appears as a localized mode at the junction of two different domain-walls. One domain-wall naturally exhibits the Stora-Zumino chain of the anomaly descent equations, starting from the axial U(1) anomaly in six-dimensions to the gauge anomaly in four-dimensions. Another domain-wall implies a similar inflow of the global anomalies. The anomaly free condition is equivalent to requiring that the axial U(1) anomaly and the parity anomaly are canceled among the six-dimensional Dirac fermions. Since our formulation is based on a massive vector-like fermion determinant, a non-perturbative regularization will be possible on a lattice. Putting the gauge field at the four-dimensional junction and extending it to the bulk using the Yang-Mills gradient flow, as recently proposed by Grabowska and Kaplan, we define the four-dimensional path integral of the target chiral gauge theory.

    ↳ hep-thhep-lathep-phPTEP(2017)·20 citations
26. 26*

    Timescales in heavy ion collisions

    Mike Lisa🇺🇸

    The study of high energy collisions between heavy nuclei is a field unto itself, distinct from nuclear and particle physics. A defining aspect of heavy ion physics is the importance of a bulk, self-interacting system with a rich space-time substructure. I focus on the issue of timescales in heavy ion collisions, starting with proof from low-energy collisions that femtoscopy can, indeed, measure very long timescales. I then discuss the relativistic case, where detailed measurements over three orders of magnitude in energy reveal a timescale increase that might be due to a first-order phase transition. I discuss also consistency in evolution timescales as determined from traditional longitudinal sizes and a novel analysis using shape information.

    ↳ nucl-thhep-phActa Phys.Polon.B(2016)·6 citations
27. 27*

    Comparison of dark energy models after Planck 2015

    Yue-Yao Xu🇺🇸 · Xin Zhang🇨🇳

    We make a comparison for ten typical, popular dark energy models according to their capabilities of fitting the current observational data. The observational data we use in this work include the JLA sample of type Ia supernovae observation, the Planck 2015 distance priors of cosmic microwave background observation, the baryon acoustic oscillations measurements, and the direct measurement of the Hubble constant. Since the models have different numbers of parameters, in order to make a fair comparison, we employ the Akaike and Bayesian information criteria to assess the worth of the models. The analysis results show that, according to the capability of explaining observations, the cosmological constant model is still the best one among all the dark energy models. The generalized Chaplygin gas model, the constant $w$ model, and the $\alpha$ dark energy model are worse than the cosmological constant model, but still are good models compared to others. The holographic dark energy model, the new generalized Chaplygin gas model, and the Chevalliear-Polarski-Linder model can still fit the current observations well, but from an economically feasible perspective, they are not so good. The new agegraphic dark energy model, the Dvali-Gabadadze-Porrati model, and the Ricci dark energy model are excluded by the current observations.

    ↳ astro-ph.COgr-qchep-phhep-thEPJC(2016)·83 citations
28. 28*

    Cosmological Tests with the FSRQ Gamma-ray Luminosity Function

    Houdun Zeng🇨🇳 · Fulvio Melia🇺🇸 · Li Zhang🇨🇳

    The extensive catalog of $\gamma$-ray selected flat-spectrum radio quasars (FSRQs) produced by \emph{Fermi} during a four-year survey has generated considerable interest in determining their $\gamma$-ray luminosity function (GLF) and its evolution with cosmic time. In this paper, we introduce the novel idea of using this extensive database to test the differential volume expansion rate predicted by two specific models, the concordance $\Lambda$CDM and $R_{\mathrm{h}}=ct$ cosmologies. For this purpose, we use two well-studied formulations of the GLF, one based on pure luminosity evolution (PLE) and the other on a luminosity-dependent density evolution (LDDE). Using a Kolmogorov-Smirnov test on one-parameter cumulative distributions (in luminosity, redshift, photon index and source count), we confirm the results of earlier works showing that these data somewhat favour LDDE over PLE; we show that this is the case for both $\Lambda$CDM and $R_{\mathrm{h}}=ct$. Regardless of which GLF one chooses, however, we also show that model selection tools very strongly favour $R_{\mathrm{h}}=ct$ over $\Lambda$CDM. We suggest that such population studies, though featuring a strong evolution in redshift, may nonetheless be used as a valuable independent check of other model comparisons based solely on geometric considerations.

    ↳ astro-ph.COastro-ph.HEgr-qchep-phMNRAS(2016)·11 citations
29. 29*

    Testing theories of Gravity and Supergravity with inflation and observations of the cosmic microwave background

    Girish Kumar Chakravarty🇮🇳 · Gaetano Lambiase🇮🇹 · Subhendra Mohanty🇮🇳

    Many extensions of Einstein's theory of gravity have been studied and proposed with various motivations like the quest for a quantum theory of gravity to extensions of anomalies in observations at the solar system, galactic and cosmological scales. These extensions include adding higher powers of Ricci curvature $R$, coupling the Ricci curvature with scalar fields and generalized functions of $R$. In addition when viewed from the perspective of Supergravity (SUGRA) many of these theories may originate from the same SUGRA theory interpreted in different frames. SUGRA therefore serves as a good framework for organizing and generalizing theories of gravity beyond General Relativity. All these theories when applied to inflation (a rapid expansion of early Universe in which primordial gravitational waves might be generated and might still be detectable by the imprint they left or by the ripples that persist today) can have distinct signatures in the Cosmic Microwave Background radiation temperature and polarization anisotropies. In this review we give a detailed discussion on the standard model of cosmology ($\Lambda$CDM), inflation and cosmological perturbation theory. We survey the theories of gravity beyond Einstein's General Relativity, specially which arise from SUGRA, and study the consequences of these theories in the context of inflation and put bounds on the theories and the parameters therein from the observational experiments like Planck, Keck/BICEP. The possibility of testing these theories in the near future in CMB observations and new data coming from colliders like the LHC, provides an unique opportunity for constructing verifiable models of particle physics and General Relativity.

    ↳ astro-ph.COgr-qchep-phInt.J.Mod.Phys.D(2017)·13 citations
30. 30*

    $\theta$ dependence of 4D $SU(N)$ gauge theories in the large-$N$ limit

    Claudio Bonati🇮🇹 · Massimo D'Elia🇮🇹 · Paolo Rossi🇮🇹 · Ettore Vicari🇮🇹

    We study the large-$N$ scaling behavior of the $\theta$ dependence of the ground-state energy density $E(\theta )$ of four-dimensional (4D) $SU(N)$ gauge theories and two-dimensional (2D) $C{P}^{N-1}$ models, where $\theta$ is the parameter associated with the Lagrangian topological term. We consider its $\theta$ expansion around $\theta =0$, $E(\theta )-E(0)=\frac{1}{2}\chi {\theta }^2(1+b_2{\theta }^2+b_4{\theta }^4+\cdots )$ where $\chi$ is the topological susceptibility and $b_{2n}$ are dimensionless coefficients. We focus on the first few coefficients $b_{2n}$, which parametrize the deviation from a simple Gaussian distribution of the topological charge at $\theta =0$. We present a numerical analysis of Monte Carlo simulations of 4D $SU(N)$ lattice gauge theories for $N=3,4,6$ in the presence of an imaginary $\theta$ term. The results provide a robust evidence of the large-$N$ behavior predicted by standard large-$N$ scaling arguments, i.e. $b_{2n}=O(N^{-2n})$. In particular, we obtain $b_2={\bar{b}}_2/N^2+O(1/N^4)$ with ${\bar{b}}_2=-0.23(3)$. We also show that the large-$N$ scaling scenario applies to 2D $C{P}^{N-1}$ models as well, by an analytic computation of the leading large-$N$ dependence.

    ↳ hep-lathep-phhep-thPRD(2016)·88 citations
31. 31*

    Mirage in Temporal Correlation functions for Baryon-Baryon Interactions in Lattice QCD

    Takumi Iritani🇺🇸 · Takumi Doi🇯🇵 · Sinya Aoki🇯🇵 · Shinya Gongyo🇫🇷 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Noriyoshi Ishii🇯🇵 · Keiko Murano🇯🇵 · Hidekatsu Nemura🇯🇵 · Kenji Sasaki🇯🇵

    Single state saturation of the temporal correlation function is a key condition to extract physical observables such as energies and matrix elements of hadrons from lattice QCD simulations. A method commonly employed to check the saturation is to seek for a plateau of the observables for large Euclidean time. Identifying the plateau in the cases having nearby states, however, is non-trivial and one may even be misled by a fake plateau. Such a situation takes place typically for the system with two or more baryons. In this study, we demonstrate explicitly the danger from a possible fake plateau in the temporal correlation functions mainly for two baryons ($\Xi \Xi$ and $NN$), and three and four baryons (${}^3\mathrm{He}$ and ${}^4\mathrm{He})$ as well, employing (2+1)-flavor lattice QCD at $m_{\pi }=0.51$ GeV on four lattice volumes with $L=$ 2.9, 3.6, 4.3 and 5.8 fm. Caution is given for drawing conclusion on the bound $NN$, $3N$ and $4N$ systems only based on the temporal correlation functions.

    ↳ hep-lathep-phnucl-thJHEP(2016)·86 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.