Tue·Jan 5, 2016Tuesday·January 5, 2016

1. 01*

   Soft $A_4\to Z_3$ Symmetry Breaking and Cobimaximal Neutrino Mixing

   Ernest Ma (UC Riverside and HKUST/JCIAS)🇺🇸

   I propose a model of radiative charged-lepton and neutrino masses with $A_4$ symmetry. The soft breaking of $A_4$ to $Z_3$ lepton triality is accomplished by dimension-three terms. The breaking of $Z_3$ by dimension-two terms allow cobimaximal neutrino mixing $({\theta }_{13}\ne 0,{\theta }_{23}=\pi /4,{\delta }_{CP}=\pm \pi /2)$ to be realized with only very small finite calculable deviations from the residual lepton triality. This construction solves a long-standing technical problem inherent in renormalizable $A_4$ models since their inception.

   hep-phPLB(2016)·50 citations
2. 02*

   Constraining Natural SUSY via the Higgs Coupling and the Muon Anomalous Magnetic Moment Measurements

   Tianjun Li🇨🇳 · Shabbar Raza🇨🇳 · Kechen Wang🇨🇳

   We use the Higgs coupling and the muon anomalous magnetic moment measurements to constrain the parameter space of the natural supersymmetry (SUSY) in the Generalized Minimal Supergravity (GmSUGRA) model. We scan the parameter space of the GmSUGRA model with small electroweak fine-tuning measure (${\Delta }_{\mathrm{EW}}\le 100$). The parameter space after applying various sparticle mass bounds, Higgs mass bounds, B-physics bounds, the muon magnetic moment constraint, and the Higgs coupling constraint from measurements at HL-LHC, ILC, and CEPC, is shown in the planes of various interesting model parameters and sparticle masses. Our study indicates that the Higgs coupling and muon anomalous magnetic moment measurements can constrain the parameter space effectively. It is shown that ${\Delta }_{\mathrm{EW}}\sim$ 30, consistence with all constraints, and having supersymmetric contributions to the muon anomalous magnetic moment within 1$\sigma$ can be achieved. The precision of $k_b$ and $k_{\tau }$ measurements at CEPC can bound $m_A$ to be above 1.2 TeV and 1.1 TeV respectively. The combination of the Higgs coupling measurement and muon anomalous magnetic moment measurement constrain ${\tilde{e}}_R$ mass to be in the range from 0.6 TeV to 2 TeV. The range of both ${\tilde{e}}_L$ and ${\tilde{\nu }}_e$ masses is 0.4 TeV $\sim$ 1.2 TeV. In all cases, the ${\tilde{\chi }}_1^0$ mass needs to be small (mostly $\le$ 400 GeV). The comparison of bounds in the $\tan \beta -m_A$ plane shows that the Higgs coupling measurement is complementary to the direct collider searches for heavy Higgs when constraining the natural SUSY. A few mass spectra in the typical region of parameter space after applying all constraints are shown as well.

   hep-phPRD(2016)·18 citations
3. 03*

   Viable Chaotic Inflation as a Source of Neutrino Masses and Leptogenesis

   Kazunori Nakayama🇯🇵 · Fuminobu Takahashi🇯🇵 · Tsutomu T. Yanagida🇯🇵

   We show that the seesaw mechanism as well as leptogenesis are natural outcomes of a viable chaotic inflation in supergravity. The inflation model contains two superfields, the inflaton and stabilizer fields, which, being singlets under the standard model gauge symmetry, naturally couple to the lepton and Higgs doublets. The inflaton decays into leptons and Higgs fields, and the reheating temperature is predicted to be of O(10^{13}) GeV, for which thermal leptogenesis is possible. On the other hand, gravitinos are copiously produced, and various solutions to the gravitino problem are discussed. We also argue that, if the shift symmetry of the inflaton is explicitly broken down to a discrete one, neutrino Yukawa couplings are periodic in the inflaton field, and masses of leptons and Higgs do not blow up even if the inflaton takes super-Planckian field values. The inflaton potential is given by a sum of sinusoidal functions with different height and periodicity, the so-called multi-natural inflation. We show that the predicted scalar spectral index and tensor-to-scalar ratio lie in the region favored by the Planck data.

   hep-phastro-ph.COPLB(2016)·18 citations
4. 04*

   Pseudoscalar Gluinonia to 750 GeV LHC Diphotons

   C.T. Potter🇺🇸

   Interpreting the diphoton mass excesses near 750~GeV reported by ATLAS and CMS as pseudoscalar gluinonia, bound states of two gluinos, we perform a scan in Next-to-Minimal Supersymmetry parameter space, fixing $m_{\tilde{g}}\approx 380$~GeV and identifying an experimentally viable point. We generate events with this point, perform fast simulation, and carry out an analysis modeled on the ATLAS search which reproduces features of the diphoton excess. This interpretation requires an enhancement of the signal strength above the nominal rate found in the literature and neglecting the gaugino mass unification constraint $M_3\approx 3M_2$.

   hep-ph40 citations
5. 05*

   The ${\rm Y}(1S)$ $\to$ $B_c\rho$ decay with perturbative QCD approach

   Junfeng Sun🇨🇳 · Yueling Yang🇨🇳 · Qingxia Li · Gongru Lu · Jinshu Huang🇨🇳 · Qin Chang🇨🇳

   With the potential prospects of the ${\rm Y}(1S)$ data samples at the running LHC and upcoming SuperKEKB, the ${\rm Y}(1S)$ $\to$ $B_c\rho$ weak decays are studied with the pQCD approach. It is found that (1) the lion's share of branching ratio comes from the longitudinal polarization helicity amplitudes; (2) branching ratio for the ${\rm Y}(1S)$ $\to$ $B_c\rho$ decay can reach up to $\mathcal{O}(10^{-9})$, which might be hopefully measurable.

   hep-phNPB(2016)·2 citations
6. 06*

   Heavy Quark and Quarkonium Transport in High Energy Nuclear Collisions

   Kai Zhou🇨🇳 · Wei Dai🇨🇳 · Nu Xu🇺🇸 · Pengfei Zhuang🇨🇳

   The strong interaction between heavy quarks and the quark gluon plasma makes the open and hidden charm hadrons be sensitive probes of the deconfinement phase transition in high energy nuclear collisions. Both the cold and hot nuclear matter effects change with the colliding energy and significantly influence the heavy quark and charmonium yield and their transverse momentum distributions. The ratio of averaged quarkonium transverse momentum square and the elliptic flow reveal the nature of the QCD medium created in heavy ion collisions at SPS, RHIC and LHC energies.

   hep-phnucl-thNPA(2016)·4 citations
7. 07*

   Vector-Like Exotics in F-Theory and 750 GeV Diphotons

   Eran Palti🇩🇪

   The recent excess in diphoton events around 750 GeV seen by the ATLAS and CMS experiments could be hinting at the existence of new vector-like charged matter around the TeV scale which couples to a singlet. Such a spectrum of exotics arises inevitably in certain classes of F-theory GUTs with hypercharge flux when the GUT symmetry is extended by a U(1) symmetry under which the Higgs fields of the MSSM are not vector-like. The exotics are not vector-like under the U(1) symmetry and therefore their mass is naturally related to its breaking scale. Previously this scale was taken to be close to the GUT scale which led to tension with proton decay, the $\mu$-term magnitude, and too large R-parity violation. The 750 GeV excess provides new motivation for considering breaking the U(1) around the TeV scale, which additionally alleviates the previous problems. We study the possible TeV-scale spectrum in such an SU(5) GUT scenario and show that it is constrained and predictive. Gauge coupling unification can be retained at the accuracy of the MSSM at one loop even though typically the spectrum does not form complete GUT representations. For example the exotics cannot form a complete 10 multiplet but nonetheless happen to behave as one in the beta functions. We present an initial analysis of the diphoton production rates for the exotics spectra and find them compatible with data.

   hep-phhep-thNPB(2016)·66 citations
8. 08*

   Massive dark photons in a Higgs portal model

   Dimiter Hadjimichef🇧🇷

   An extension of the Standard Model with a hidden sector which consists of gauge singlets (a Dirac fermion $\chi$ and a scalar $S$) plus a vector boson $V_{\mu }$ (dark massive photon) is studied. The singlet scalar interacts with the Standard Model sector through the triple and quartic scalar interactions, while the singlet fermion and vector boson field interact with the Standard Model only via the singlet scalar. The scalar field generates the vector boson's mass. Perspectives for future $e^{-}{e}^{+}$ colliders is considered.

   hep-phnucl-thAIP Conf.Proc.(2015)·3 citations
9. 09*

   Zero energy scattering calculation in Euclidean space

   J. Carbonell🇫🇷 · V.A. Karmanov🇷🇺

   We show that the Bethe-Salpeter equation for the scattering amplitude in the limit of zero incident energy can be transformed into a purely Euclidean form, as it is the case for the bound states. The decoupling between Euclidean and Minkowski amplitudes is only possible for zero energy scattering observables and allows determining the scattering length from the Euclidean Bethe-Salpeter amplitude. Such a possibility strongly simplifies the numerical solution of the Bethe-Salpeter equation and suggests an alternative way to compute the scattering length in Lattice Euclidean calculations without using the Luscher formalism. The derivations contained in this work were performed for scalar particles and one-boson exchange kernel. They can be generalized to the fermion case and more involved interactions.

   hep-phhep-lathep-thnucl-thPLB(2016)·9 citations
10. 10*

    The Roots of the Standard Model of Particle Physics

    P.J. Mulders🇳🇱

    We conjecture how the particle content of the standard model can emerge starting with a supersymmetric Wess-Zumino model in 1+1 dimensions (d = 2) with three real boson and fermion fields. Considering SU(3) transformations, the lagrangian and its ground state are SO(3) invariant. The SO(3) symmetry extends the basic IO(1,1) Poincaré symmetry to IO(1,3) for the asymptotic fields requiring physical states to be singlets under the A_4 symmetry that governs the SO(3) embedding. This is linked to the three-family structure. For the internal symmetries of the asymptotic fields an SU(2) x U(1) symmetry remains, broken down as in the standard model. The boson excitations in d = 4 are identified with electroweak gauge bosons and the Higgs boson. Fermion excitations come in three families of leptons living in E(1,3) Minkowski space or three families of quarks living in E(1,1). Many features of the standard model now emerge in a natural way. The supersymmetric starting point solves the naturalness problem. The underlying left-right symmetry leads to custodial symmetry in the electroweak sector. In the spectrum one has Dirac-type charged leptons and Majorana-type neutrinos. The electroweak behavior of the naturally confined quarks, leads to fractional electric charges and the doublet and singlet structure of left- and right-handed quarks, respectively. Most prominent feature is the link between the number of colors, families and space directions.

    hep-ph4 citations
11. 11*

    Extending the MSSM with singlet Higgs and right handed neutrino for the self-interacting dark matter

    Hai-Jing Kang🇰🇷 · Wenyu Wang🇨🇳

    In order to meet the requirement of BBN, the right handed neutrino is added to the singlet Higgs sector in the GNMSSM. The spectrum and Feynman rules are calculated. the dark matter phenomenology is also studied. In case of $\text{l}\sim 0$, the singlet sector can give perfect explanation of relic abundance of dark matter and small cosmological structure simulations. The BBN constraints on the light mediator can be easily solved by decaying to the right handed neutrino. When the ${\text{l}}_N$ is at the order of $\mathcal{O}(0.1)$, the mass of the mediator can be constrained to several MeV

    hep-phCommun.Theor.Phys.(2016)·8 citations
12. 12*

    Four-loop Neutrino Model Inspired by Diphoton Excess at 750 GeV

    Takaaki Nomura🇰🇷 · Hiroshi Okada🇹🇼

    We propose a four-loop induced radiative neutrino mass model inspired by the diphoton excess at 750 GeV recently reported by ATLAS and CMS, in which a sizable diphoton excess is obtained via photon fusion introducing multi doubly-charged scalar bosons. Also we discuss the muon anomalous magnetic moment, and a dark matter candidate. The main process to explain the observed relic density relies on the final state of the new particle at 750 GeV. Finally we show the numerical results and obtain allowed region of several physical values in our model.

    hep-phhep-exPLB(2016)·74 citations
13. 13*

    Higgs boson decay to two photons and the dispersion relations

    Kirill Melnikov🇩🇪 · Arkady Vainshtein🇺🇸

    We discuss the computation of the Higgs boson decay amplitude to two photons through the W-loop using dispersion relations. The imaginary part of the form factor F_W(s) that parametrizes this decay is unambiguous in four dimensions. When it is used to calculate the unsubtracted dispersion integral, the finite result for the form factor F_W(s) is obtained. However, the F_W(s) obtained in this way differs by a constant term from the result of a diagrammatic computation, based on dimensional regularization. It is easy to accommodate the missing constant by writing a once-subtracted dispersion relation for F_W(s) but it is unclear why the subtraction needs to be done. The goal of this paper is to investigate this question in detail. We show that the correct constant can be recovered within a dispersive approach in a number of ways that, however, either require an introduction of an ultraviolet regulator or unphysical degrees of freedom; unregulated and unsubtracted computations in the unitary gauge are insufficient, in spite of the fact that such computations give a finite result.

    hep-phPRD(2016)·16 citations
14. 14*

    A possible relation between leptogenesis and PMNS phases

    Laura Covi🇩🇪 · Jihn E. Kim🇰🇷 · Bumseok Kyae🇰🇷 · Soonkeon Nam🇰🇷

    We propose a new scenario for baryogenesis through leptogenesis, where the CP phase relevant for leptogenesis is connected directly to the PMNS phase(s) in the light neutrino mixing matrix. The scenario is realized in case only one CP phase appears in the full theory, originating from the complex vacuum expextation value of a standard model singlet field. In order to realize this scheme, the electroweak symmetry is required to be broken during the leptogenesis era and a new loop diagram with an intermediate $W$ boson exchange including the low energy neutrino mixing matrix should play the dominant contribution to the CP violation for leptogenesis. In this letter, we discuss the new basic mechanism, which we call type-II leptogenesis, and give an estimate for maximally reachable baryon asymmetry depending on the PMNS phases.

    hep-phastro-ph.COPRD(2016)·13 citations
15. 15*

    Analytical results for non-linear Compton scattering in short intense laser pulses

    Daniel Seipt🇩🇪 · Vasily Kharin🇩🇪 · Sergey Rykovanov🇩🇪 · Andrey Surzhykov🇩🇪 · Stephan Fritzsche🇩🇪

    We study in detail the strong-field QED process of non-linear Compton scattering in short intense plane wave laser pulses of circular polarization. Our main focus is placed on how the spectrum of the back-scattered laser light depends on the shape and duration of the initial short intense pulse. Although this pulse shape dependence is very complicated and highly non-linear, and has never been addressed explicitly, our analysis reveals that all the dependence on the laser pulse shape is contained in a class of three-parameter master integrals. Here we present completely analytical expressions for the non-linear Compton spectrum in terms of these master integrals. Moreover, we analyse the universal behaviour of the shape of the spectrum for very high harmonic lines.

    hep-phphysics.atom-phphysics.plasm-phJ.Plasma Phys.(2016)·48 citations
16. 16*

    Higgs boson production in the $U(1{)}_{B-L}$ model at the ILC

    Jinzhong Han🇨🇳 · Bingfang Yang🇨🇳 · Ning Liu🇨🇳 · Jitao Li🇨🇳

    In the framework of the minimal $U(1{)}_{B-L}$ extension of the Standard Model, we investigate the Higgs boson production processes $e^{+}{e}^{-}\to ZH$, $e^{+}{e}^{-}\to {\nu }_e\overline{{\nu }_e}H$, $e^{+}{e}^{-}\to t\bar{t}H$, $e^{+}{e}^{-}\to ZHH$ and $e^{+}{e}^{-}\to {\nu }_e\overline{{\nu }_e}HH$ at the International Linear Collider (ILC). We present the production cross sections, the relative corrections and compare our results with the expected experimental accuracies for Higgs decay channel $H\to b\bar{b}$. In the allowed parameter space, we find that the effects of the three single Higgs boson production processes might approach the observable threshold of the ILC, and that the Higgs signal strengths ${\mu }_{b\bar{b}}$ of the two double Higgs boson production processes are all out of the observable threshold of the ILC so that the effects will be difficult to be observed at the ILC.

    hep-phInt.J.Mod.Phys.A(2016)·2 citations
17. 17*

    Are there any clues for hadron asymptotics in the LHC data?

    S.M. Troshin🇷🇺 · N.E. Tyurin🇷🇺

    We discuss several clues related to the possible asymptotic behavior of hadron interactions arising on the base of performed analysis of the recent TOTEM data at the LHC and emphasize that the deep-elastic scattering can provide an important information on the asymptotical dependence via the unitarity relation.

    hep-ph4 citations
18. 18*

    The property of maximal transcendentality: calculation of Feynman integrals

    A.V. Kotikov🇷🇺

    We review some results of calculations, having the property of maximal transcendentality.

    hep-phhep-thTheor.Math.Phys.(2017)·7 citations
19. 19*

    Explaining 750 GeV diphoton excess from top/bottom partner cascade decay in two-Higgs-doublet model extension

    Xiao-Fang Han🇨🇳 · Lei Wang🇨🇳 · Lei Wu🇦🇺 · Jin Min Yang🇨🇳 · Mengchao Zhang🇨🇳

    In this paper, we interpret the 750 GeV diphoton excess in the Zee-Babu extension of the two-Higgs-doublet model by introducing a top partner ($T$)/bottom partner ($B$). In the alignment limit, the 750 GeV resonance is identified as the heavy CP-even Higgs boson ($H$), which can be sizably produced via the QCD process $pp\to T\bar{T}$ or $pp\to B\bar{B}$ followed by the decay $T\to Ht$ or $B\to Hb$. The diphoton decay rate of $H$ is greatly enhanced by the charged singlet scalars predicted in the Zee-Babu extension and the total width of $H$ can be as large as 7 GeV. Under the current LHC constraints, we scan the parameter space and find that such an extension can account for the observed diphoton excess.

    hep-phPLB(2016)·61 citations
20. 20*

    Exotic resonances due to $\eta$ exchange

    Marek Karliner🇮🇱 · Jonathan L. Rosner🇺🇸

    The meson $X(3872)$ and several related states appear to be, at least in part, hadronic molecules in which a heavy flavored meson (such as $D^0$) is bound to another heavy meson (such as ${\bar{D}}^{\ast 0}$). Although not the only effect contributing to the binding, pion exchange seems to play a crucial role in generating the longest-range force between constituents. Mesons without $u$ and $d$ light quarks (such as $D_s$) cannot exchange pions, but under suitable circumstances can bind as a result of $\eta$ exchange. Channels in which this mechanism is possible are identified, and suggestions are made for searches for the corresponding molecular states, including a manifestly exotic baryonic ${\Lambda }_c{\bar{D}}_s^{\ast }$ resonance decaying into $J/\psi \Lambda$.

    hep-phhep-exNPA(2016)·50 citations
21. 21*

    Renormalization Group Summation with Heavy Fields

    D.G.C. McKeon🇨🇦

    The summation of logarithmic contributions to perturbative radiative corrections in physical processes through use of the renormalization group equation has proved to be a useful way of enhancing the information one can obtain from explicit calculation. However, it has proved difficult to perform this summation when massive fields are present. In this note we point out that if the masses involved are quite large, the decoupling theorem of Symanzik and of Appelquist and Carazzone can be used to make the summation of logarithms possible.

    hep-phhep-thCan.J.Phys.(2018)·1 citation
22. 22*

    Axions at the International Axion Observatory

    Javier Redondo🇪🇸

    QCD axions with meV mass can be behind some stellar cooling anomalies and form all or part of the cold dark matter of the universe. We discuss on a proposed experiment to discover the solar flux of meV mass axions: the International AXion Observatory: IAXO.

    hep-phastro-ph.COastro-ph.SR1 citation
23. 23*

    Diphoton Excess at 750 GeV in leptophobic U(1)${}^{\prime }$ model inspired by $E_6$ GUT

    P. Ko🇰🇷 · Yuji Omura🇯🇵 · Chaehyun Yu🇹🇼

    We discuss the 750 GeV diphoton excess at the LHC@13TeV in the framework of leptophobic U(1)${}^{\prime }$ model inspired by $E_6$ grand unified theory (GUT). In this model, the Standard Model (SM) chiral fermions carry charges under extra U(1)${}^{\prime }$ gauge symmetry which is spontaneously broken by a U(1)${}^{\prime }$-charged singlet scalar ($\Phi$). In addition, extra quarks and leptons are introduced to achieve the anomaly-free conditions, which is a natural consequence of the assumed $E_6$ GUT. These new fermions are vectorlike under the SM gauge group but chiral under new U(1)${}^{\prime }$, and their masses come entirely from the nonzero vacuum expectation value of $\Phi$ through the Yukawa interactions. Then, the CP-even scalar $h_{\Phi }$ from $\Phi$ can be produced at the LHC by the gluon fusion and decay to the diphoton via the one-loop diagram involving the extra quarks and leptons, and can be identified as the origin of diphoton excess at 750 GeV. In this model, $h_{\Phi }$ can decay into a pair of dark matter particles as well as a pair of scalar bosons, thereby a few tens of the decay width may be possible.

    hep-phhep-exJHEP(2016)·72 citations
24. 24*

    The LHC upper bounds for $pp\to \text{diboson}$, $t\bar{t}$ cross section on fermionic dark matter

    Karim Ghorbani (Arak U.)🇮🇷 · Parsa Hossein Ghorbani (IPM, Tehran)🇮🇷

    The ATLAS report in August 2016 provided an upper limit for the $pp\to$ diboson and $t\bar{t}$ cross sections. We consider a pseudoscalar-mediated fermionic dark matter together with gluon and photon effective operators interacting with the pseudoscalar. Choosing the resonance mass being $m_{\rho }=200,750$ GeV and $2$ TeV, beside the relic density and the invisible Higgs decay constraints we constrain more the space of parameters with the diboson and $t\bar{t}$ cross section upper bounds. We finally provide some benchmarks consistent with all the constraints. Having exploited a pseudoscalar mediator, the DM-nucleon cross section is velocity suppressed so that the model evades easily the bounds put by the future direct detection experiments such as XENON1T.

    hep-phInt.J.Mod.Phys.A(2017)·62 citations
25. 25*

    Renormalized coupling constants for 3D scalar \lambda\phi^4 field theory and pseudo-\epsilon-expansion

    M. A. Nikitina🇷🇺 · A. I. Sokolov🇷🇺

    Renormalized coupling constants g_{2k} that enter the critical equation of state and determine nonlinear susceptibilities of the system possess universal values g*_{2k} at the Curie point. They are calculated, along with the ratios R_{2k} = g_{2k}/g_4^{k-1}, for the three-dimensional scalar \lambda\phi^4 field theory within the pseudo-\epsilon-expansion approach. Pseudo-\epsilon-expansions for g*_6, g*_8, R*_6, and R*_8 are derived in the five-loop approximation, numerical estimates are presented for R*_6 and R*_8. The higher-order coefficients of the pseudo-\epsilon-expansions for the sextic coupling are so small that simple Pade approximants turn out to be sufficient to yield very good numerical results. Their use gives R*_6 = 1.650 while the most recent lattice estimate is R*_6 = 1.649(2). For the octic coupling pseudo-\epsilon-expansions are less favorable from the numerical point of view. Nevertheless, Pade-Borel resummation leads in this case to R*_8 = 0.890, the number differing only slightly from the values R*_8 = 0.871, R*_8 = 0.857 extracted from the lattice and field-theoretical calculations.

    ↳ hep-thcond-mat.softcond-mat.stat-mechhep-lat+1Theor.Math.Phys.(2017)·0 citations
26. 26*

    Color transparency in ${\pi }^{-}$-induced dilepton production on nuclei

    A.B. Larionov🇩🇪 · M. Strikman🇺🇸 · M. Bleicher🇩🇪

    We argue that the observation of the color transparency effect in the semiexclusive $A({\pi }^{-},l^{+}{l}^{-})$ process is important for determining whether it is possible to extract the generalized parton distributions of the nucleon from the elementary reaction ${\pi }^{-}p\to l^{+}{l}^{-}n$ at $p_{\mathrm{lab}}=15-20$ GeV/c at small $|t|$ and large invariant mass of the dilepton pair $l^{+}{l}^{-}$. Assuming that the transverse size of the pionic $q\bar{q}$ pair in the hard interaction point is similar to the one in the reaction ${\gamma }^{\ast }p\to {\pi }^{+}n$ studied at JLab we predict large color transparency effects in the discussed kinematic range. We also suggest that the semiexclusive ${\rho }^0$ production in ${\pi }^{-}$-induced reactions in the same beam momentum region may provide new information on the dynamics of the interaction in the non-vacuum channel, while the $J/\psi$ production can be used to get information on $J/\psi N$ total interaction cross section.,

    ↳ nucl-thhep-exhep-phnucl-exPRC(2016)·10 citations
27. 27*

    Fluctuations in a Cosmology with a Space-Like Singularity and their Gauge Theory Dual Description

    Robert H. Brandenberger🇨🇦 · Yi-Fu Cai🇨🇳 · Sumit R. Das🇺🇸 · Elisa G.M. Ferreira🇨🇦 · Ian A. Morrison🇨🇦 · Yi Wang🇨🇳

    We consider a time-dependent deformation of anti-de-Sitter (AdS) space-time which contains a cosmological "singularity" - a space-like region of high curvature. Making use of the AdS/CFT correspondence we can map the bulk dynamics onto the boundary. The boundary theory has a time dependent coupling constant which becomes small at times when the bulk space-time is highly curved. We investigate the propagation of small fluctuations of a test scalar field from early times before the bulk singularity to late times after the singularity. Under the assumption that the AdS/CFT correspondence extends to deformed AdS space-times, we can map the bulk evolution of the scalar field onto the evolution of the boundary gauge field. The time evolution of linearized fluctuations is well defined in the boundary theory as long as the coupling remains finite, so that we can extend the boundary perturbations to late times after the singularity. Assuming that the spacetime in the future of the singularity has a weakly coupled region near the boundary, we reconstruct the bulk fluctuations after the singularity crossing making use of generic properties of boundary-to-bulk propagators. Finally, we extract the spectrum of the fluctuations at late times given some initial spectrum. We find that the spectral index is unchanged, but the amplitude increases due to the squeezing of the fluctuations during the course of the evolution. This investigation can teach us important lessons on how the spectrum of cosmological perturbations passes through a bounce which is singular from the bulk point of view but which is resolved using an ultraviolet complete theory of quantum gravity.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2016)·30 citations
28. 28*

    Chiral Magnetic Effect in Heavy Ion Collisions

    Jinfeng Liao🇺🇸

    The Chiral Magnetic Effect (CME) is a remarkable phenomenon that stems from highly nontrivial interplay of QCD chiral symmetry, axial anomaly, and gluonic topology. It is of fundamental importance to search for the CME in experiments. The heavy ion collisions provide a unique environment where a hot chiral-symmetric quark-gluon plasma is created, gluonic topological fluctuations generate chirality imbalance, and very strong magnetic fields $|\vec{\mathbf{B}}|\sim m_{\pi }^2$ are present during the early stage of such collisions. Significant efforts have been made to look for CME signals in heavy ion collision experiments. In this contribution we give a brief overview on the status of such efforts.

    ↳ nucl-thhep-phnucl-exNPA(2016)·20 citations
29. 29*

    Critical scaling in the large-$N$ $O(N)$ model in higher dimensions and its possible connection to quantum gravity

    P. Mati🇭🇺

    The critical scaling of the large-$N$ $O(N)$ model in higher dimensions using the exact renormalization group equations has been studied, motivated by the recently found non-trivial fixed point in $4<d<6$ dimensions with metastable critical potential. Particular attention is paid to the case of $d=5$ where the scaling exponent $\nu$ has the value $1/3$, which coincides with the scaling exponent of quantum gravity in one fewer dimensions. Convincing results show that this relation could be generalized to arbitrary number of dimensions above five. Some aspects of AdS/CFT correspondence are also discussed.

    ↳ hep-thcond-mat.stat-mechhep-phPRD(2016)·26 citations
30. 30*

    Solitons in an effective theory of CP violation

    N. Chandra🇮🇳 · M. B. Paranjape🇨🇦 · R. Srivastava🇮🇳

    We study an effective field theory describing CP-violation in a scalar meson sector. We write the simplest interaction that we can imagine, $$\mathcal{L}\sim {ϵ}_{i_1\cdots i_5}{ϵ}^{{\mu }_1\cdots {\mu }_4}{\varphi }_{i_1}{\partial }_{{\mu }_1}{\varphi }_{i_2}{\partial }_{{\mu }_2}{\varphi }_{i_3}{\partial }_{{\mu }_3}{\varphi }_{i_4}{\partial }_{{\mu }_4}{\varphi }_{i_5}$$ which involves 5 scalar fields. The theory describes CP-violation only when it contains scalar fields representing mesons such as the $K_0^{\ast }$, sigma, $f_0$ or $a_0$. If the fields represent pseudo-scalar mesons, such as B, K and $\pi$ mesons then the Lagrangian describes anomalous processes such as $KK\to \pi \pi \pi$. We speculate that the field theory contains long lived excitations corresponding to $Q$-ball type domain walls expanding through space-time. In an 1+1 dimensional, analogous, field theory we find an exact, analytic solution corresponding to such solitons. The solitons have a U(1) charge $Q$, which can be arbitrarily high, but oddly, the energy behaves as $Q^{2/3}$ for large charge, thus the configurations are stable under disintegration into elementary charged particles of mass $m$ with $Q=1$. We also find analytic complex instanton solutions which have finite, positive Euclidean action.

    ↳ hep-thhep-ph0 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.