Mon·Nov 28, 2016Monday·November 28, 2016

1. 01*

   Scattering of wave packets with phases

   Dmitry Karlovets🇷🇺

   A general problem of $2\to N_f$ scattering is addressed with all the states being wave packets with arbitrary phases. Depending on these phases, one deals with coherent states in $(3+1)$ D, vortex particles with orbital angular momentum, the Airy beams, and their generalizations. A method is developed in which a number of events represents a functional of the Wigner functions of such states. Using width of a packet ${\sigma }_p/⟨p⟩$ as a small parameter, the Wigner functions, the number of events, and a cross section are represented as power series in this parameter, the first non-vanishing corrections to their plane-wave expressions are derived, and generalizations for beams are made. Although in this regime the Wigner functions turn out to be everywhere positive, the cross section develops new specifically quantum features, inaccessible in the plane-wave approximation. Among them is dependence on an impact parameter between the beams, on phases of the incoming states, and on a phase of the scattering amplitude. A model-independent analysis of these effects is made. Two ways of measuring how a Coulomb phase and a hadronic one change with a transferred momentum $t$ are discussed.

   hep-phmath-phmath.MPquant-phJHEP(2017)·51 citations
2. 02*

   Sparticle spectroscopy of the minimal SO(10) model

   Takeshi Fukuyama🇯🇵 · Nobuchika Okada🇺🇸 · Hieu Minh Tran🇻🇳

   The supersymmetric (SUSY) minimal SO(10) model is a well-motivated grand unified theory, where the Standard Model (SM) fermions have Yukawa couplings with only one $10$-plet and one $\overline{126}$-plet Higgs fields and it is highly non-trivial if the realistic quark and lepton mass matrices can be reproduced in this context. It has been known that the best fit for all the SM fermion mass matrices is achieved by a vacuum expectation value of the $\overline{126}$-plet Higgs field being at the intermediate scale of around $\mathcal{O}(10^{13})$ GeV. Under the presence of the SO(10) symmetry breaking at the intermediate scale, the successful SM gauge coupling unification is at risk and likely to be spoiled. Recently, it has been shown that the low-energy fermion mass matrices, except for the down-quark mass predicted to be too low, are very well-fitted without the intermediate scale. In order to resolve the too-low down quark mass while keeping the other fittings intact, we consider SUSY threshold corrections to reproduce the right down quark mass. It turns out that this requires flavor-dependent soft parameters. Motivated by this fact, we calculate particle mass spectra at low energies with flavor-dependent sfermion masses at the grand unification scale. We present a benchmark particle mass spectrum which satisfies a variety of phenomenological constraints, in particular, the observed SM-like Higgs boson mass of around 125 GeV and the relic abundance of the neutralino dark matter as well as the experimental result of the muon anomalous magnetic moment. In the resultant mass spectrum, sleptons in the first and second generations, bino and winos are all light, and this scenario can be tested at the LHC Run-2 in the near future.

   hep-phPLB(2017)·23 citations
3. 03*

   Axion and Neutrino physics in a $U(1)$-enhanced supersymmetric model

   Y. H. Ahn🇰🇷

   Motivated by the flavored Peccei-Quinn symmetry for unifying the flavor physics and string theory, we construct an explicit model by introducing a $U(1)$ symmetry such that the $U(1{)}_X$-$[gravity{]}^2$ anomaly-free condition together with the standard model flavor structure demands additional sterile neutrinos as well as no axionic domain-wall problem. Such additional sterile neutrinos play the role of a realization of baryogenesis via a new Affleck-Dine leptogenesis. We provide grounds for that the $U(1{)}_X$ symmetry could be interpreted as a fundamental symmetry of nature. The model will resolve rather recent, but fast-growing issues in astro-particle physics, including leptonic mixings and CP violation in neutrino oscillation, high-energy neutrinos, QCD axion, and axion cooling of stars. The QCD axion decay constant, through its connection to the astrophysical constraints of stellar evolution and the SM fermion masses, is shown to be fixed at $F_A=1.30_{-0.54}^{+0.66}\times 10^9$ GeV (consequently, its mass is $m_a=4.34_{-1.49}^{+3.37}$ meV and axion-photon coupling is $|g_{a\gamma \gamma }|=1.30_{-0.45}^{+1.01}\times 10^{-12}{\mathrm{GeV}}^{-1}$). Interestingly enough, we show that neutrino oscillations at low energies could be connected to astronomical-scale baseline neutrino oscillations. The model predicts non-observational neutrinoless double beta ($0\nu \beta \beta$) decay rate as well as a remarkable pattern between leptonic Dirac CP phase (${\delta }_{CP}$) and atmospheric mixing angle (${\theta }_{23}$); {\it e.g.} ${\delta }_{CP}\simeq 220^{\circ }-240^{\circ }$, $120^{\circ }-140^{\circ }$ for ${\theta }_{23}=42.3^{\circ }$ for normal mass ordering, and ${\delta }_{CP}\simeq 283^{\circ },250^{\circ },100^{\circ },70^{\circ }$ for ${\theta }_{23}=49.5^{\circ }$ for inverted one.

   hep-phPRD(2017)·13 citations
4. 04*

   Bulk viscous corrections to screening and damping in QCD at high temperatures

   Qianqian Du🇨🇳 · Adrian Dumitru🇺🇸 · Yun Guo🇨🇳 · Michael Strickland🇺🇸

   Non-equilibrium corrections to the distribution functions of quarks and gluons in a hot and dense QCD medium modify the "hard thermal loops" (HTL). The HTLs determine the retarded, advanced, and symmetric (time-ordered) propagators for gluons with soft momenta as well as the Debye screening and Landau damping mass scales. We compute such corrections to a thermal as well as to a non-thermal fixed point.The screening and damping mass scales are sensitive to the bulk pressure and hence to (pseudo-) critical dynamical scaling of the bulk viscosity in the vicinity of a second-order critical point. This could be reflected in the properties of quarkonium bound states in the deconfined phase and in the dynamics of soft gluon fields.

   hep-phhep-thnucl-thJHEP(2017)·32 citations
5. 05*

   Improved analysis of the (O_7, O_7) contribution to $\bar{B}\to X_s\gamma \gamma$ at $O({\alpha }_s)$

   H. M. Asatrian🇦🇲 · C. Greub🇨🇭 · A. Kokulu🇬🇧

   The present study is devoted for an improved analysis of the self-interference contribution of the electromagnetic dipole operator O_7 to the double differential decay width $d\Gamma /(d{s}_{1}d{s}_2)$ for the inclusive $\bar{B}\to X_s\gamma \gamma$ process, where the kinematical variables s_1 and s_2 are defined as s_i=(p_b - q_i)^2/m_b^2 with p_b, q_1, q_2 being the momenta of the b-quark and two photons. This calculation completes the NLL QCD prediction of the numerically important self-interference contribution of O_7 by keeping the full dependence on the strange-quark mass m_s, which is introduced to control possible collinear configurations of one of the photons with the strange quark. Our results are given for exact m_s, in contrast to an earlier work where only logarithmic and constant terms in m_s were retained. This improved NLL result for the (O_7, O_7)-interference contribution shows that finite m_s effects are only sizable near the kinematical endpoints of the spectrum $d\Gamma /(d{s}_{1}d{s}_2)$. At the level of the branching ratio, in the phase-space region considered in this paper, it is observed that $Br[\bar{B}\to X_s\gamma \gamma ]$ does not develop a sizable m_s dependence: the impact on this branching ratio is less than 5% when m_s is varied between 400-600 MeV. For the same phase-space region finite strange quark mass effects for the branching ratio are less than 7%.

   hep-phhep-exPRD(2017)·4 citations
6. 06*

   Discriminating sterile neutrinos and unitarity violation with CP invariants

   Heinrich Päs🇩🇪 · Philipp Sicking🇩🇪

   We present a new method to analyze upcoming results in the search for CP violating neutrino oscillations. The CP violating amplitudes ${\mathcal{A}}_{\alpha \beta }^{kj}$ provide parametrization independent observables, which will be accessible by experiments soon. The strong prediction of a unique ${\mathcal{A}}_{\alpha \beta }^{kj}$ (the Jarlskog invariant) in case of the standard three neutrino model does not hold in models with new physics beyond the Standard Model. Nevertheless there are still correlations among the amplitudes depending on the specific model. Due to these correlations it is possible to reject specific new physics models by determining only 3 of the CP violating amplitudes.

   hep-phPRD(2017)·13 citations
7. 07*

   $\eta$-$\gamma$ and ${\eta }^{\prime }$-$\gamma$ transition form factors in a nonlocal NJL model

   D. Gomez Dumm🇦🇷 · S. Noguera🇪🇸 · N.N. Scoccola🇦🇷

   We study the $\eta$ and ${\eta }^{\prime }$ distribution amplitudes (DAs) in the context of a nonlocal SU(3)_L x SU(3)_R chiral quark model. The corresponding Lagrangian allows to reproduce the phenomenological values of pseudoscalar meson masses and decay constants, as well as the momentum dependence of the quark propagator arising from lattice calculations. It is found that the obtained DAs have two symmetric maxima, which arise from new contributions generated by the nonlocal character of the interactions. These DAs are then applied to the calculation of the $\eta$-$\gamma$ and ${\eta }^{\prime }$-$\gamma$ transition form factors. Implications of our results regarding higher twist corrections and/or contributions to the transition form factors originated by gluon-gluon components in the $\eta$ and ${\eta }^{\prime }$ mesons are discussed.

   hep-phPRD(2017)·6 citations
8. 08*

   Constraints on $L_{\mu }-L_{\tau }$ Gauge Interactions from Rare Kaon Decay

   Masahiro Ibe🇯🇵 · Wakutaka Nakano🇯🇵 · Motoo Suzuki🇯🇵

   A model with $L_{\mu }-L_{\tau }$ gauge symmetry is the least constrained model as a resolution to the disagreement of the muon anomalous magnetic moment between the theoretical predictions and the experimental results. In this paper, we discuss how well the $L_{\mu }-L_{\tau }$ model can be constrained by looking for decays of the charged kaon associated with a $L_{\mu }-L_{\tau }$ gauge boson. More concretely, we consider searches for single muon tracks from the decays of stopped charged kaon as in the E949 experiment. In our conservative estimation, we find that the favored parameter region for the muon anomalous magnetic moment can be tested by using a $10$ times larger number of the stopped charged kaons and about a $100$ times better photon rejection rate than the E949 experiment.

   hep-phPRD(2017)·42 citations
9. 09*

   Leptogenesis: Improving predictions for experimental searches

   Marco Drewes🇩🇪 · Bjorn Garbrecht🇩🇪 · Dario Gueter🇩🇪 · Juraj Klaric🇩🇪

   Heavy right handed neutrinos could not only explain the observed neutrino masses via the seesaw mechanism, but also generate the baryon asymmetry of the universe via leptogenesis due to their CP-violating interactions in the early universe. We review recent progress in the theoretical description of this nonequilibrium process. Improved calculations are particularly important for a comparison with experimental data in testable scenarios with Majorana masses below the TeV scale, in which the heavy neutrinos can be found at the LHC, in the NA62 experiment, at T2K or in future experiments, including SHiP, DUNE and experiments at the FCC, ILC or CEPC. In addition, the relevant source of CP-violation may be experimentally accessible, and the heavy neutrinos can give a sizable contribution to neutrinoless double $\beta$ decay. In these low scale leptogenesis scenarios, the matter-antimatter asymmetry is generated at temperatures when the heavy neutrinos are relativistic, and thermal corrections to the transport equations in the early universe are large.

   hep-phastro-ph.COhep-exPoS(2017)·2 citations
10. 10*

    A top-squark hunter's guide

    Howard Baer🇺🇸 · Vernon Barger🇺🇸 · Natsumi Nagata🇯🇵 · Michael Savoy🇺🇸

    In supersymmetric models with radiatively-driven naturalness and light higgsinos, the top squarks may lie in the 0.5- 3TeV range and thus only a fraction of natural parameter space is accessible to LHC searches. We outline the range of top squark and lightest SUSY particle masses preferred by electroweak naturalness in the standard parameter space plane. We note that the branching fraction for b-> s\gamma decay favors top squarks much heavier than 500 GeV. Such a range of top-squark mass values is in contrast to previous expectations where m(stop)<500 GeV had been considered natural. In radiative natural SUSY, top squarks decay roughly equally via t1-> bW1 and Z_{1,2} where W1 and Z_{1,2} are higgsino-like electroweak-inos. Thus, top squark pair production should yield all of t\bar{t}+\eslt, t\bar{b}+\eslt, b\bar{t}+\eslt and b\bar{b}+\eslt signatures at comparable rates. We propose that future LHC top squark searches take place within a semi-simplified model which corresponds more closely to expectations from theory.

    hep-phPRD(2017)·34 citations
11. 11*

    Testing CP-Violation in the Scalar Sector at Future $e^{+}{e}^{-}$ Colliders

    Gang Li🇨🇳 · Ying-nan Mao🇨🇳 · Chen Zhang🇨🇳 · Shou-hua Zhu🇨🇳

    We propose a {\em model-independent} method to test CP-violation in the scalar sector through measuring the inclusive cross sections of $e^{+}{e}^{-}\to Z{h}_1,Z{h}_2,h_1{h}_2$ processes with the recoil mass technique, where $h_1,h_2$ stand for the 125 GeV standard model (SM) like Higgs boson and a new lighter scalar respectively. This method effectively measures a quantity $K$ proportional to the product of the three couplings of $h_{1}ZZ,h_{2}ZZ,h_1{h}_{2}Z$ vertices. The value of $K$ encodes a part of information about CP-violation in the scalar sector. We simulate the signal and backgrounds for the processes mentioned above with $m_2=40\text{GeV}$ at the Circular Electron-Positron Collider (CEPC) with the integrated luminosity $5{\text{ab}}^{-1}$. We find that the discovery of both $Z{h}_2$ and $h_1{h}_2$ processes at $5\sigma$ level will indicate an $\mathcal{O}(10^{-2})$ $K$ value which can be measured to $16\%$ precision. The method is applied to the weakly-coupled Lee model in which CP-violation can be tested either before or after utilizing a "$p_T$ balance" cut (see \autoref{simu} for the definition). Lastly we point out that $K\ne 0$ is a sufficient but not a necessary condition for the existence of CP-violation in the scalar sector, namely $K=0$ does not imply CP conservation in the scalar sector.

    hep-phPRD(2017)·11 citations
12. 12*

    From $J/\psi$ to LHCb pentaquark

    F. Fernández🇪🇸 · D. R. Entem🇪🇸 · P. G. Ortega🇪🇸 · J. Segovia🇩🇪

    The original charmonium two-body problem, like the $c\bar{c}$ structure of the $J/\psi$ meson, has become more involved in the last few years with the discovery of new resonances such as the tentative molecular state $X(3872)$ or the possible pentaquark one $P_c(4380{)}^{+}$. We discuss herein how these exotic states (and others) can be described in a unified way adding higher Fock state components to the naive quark model picture. In particular, we present our theoretical results on the pentaquark states $P_c(4380{)}^{+}$ and $P_c(4450{)}^{+}$, and on the new charmonium-like resonances $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$ that have been reported in $2016$ by the LHCb Collaboration.

    hep-phhep-exhep-latnucl-th0 citations
13. 13*

    From $J/\psi$ to LHCb pentaquarks

    F. Fernández🇪🇸 · D. R. Entem🇪🇸 · P. G. Ortega🇪🇸 · J. Segovia🇩🇪

    The two exotic $P_c^{+}(4380)$ and $P_c^{+}(4450)$ discovered in $2015$ by the LHCb Collaboration, together with the four resonances $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$, reported in $2016$ by the same collaboration, are described in a constituent quark model which has been able to explain the properties of charmonium states from the $J/\psi$ to the $X(3872)$. Using this model we found a $\bar{D}{\Sigma }_c^{\ast }$ bound state with $J^P={\frac{3}{2}}^{-}$ that may be identified with the $P_c^{+}(4380)$. In the ${\bar{D}}^{\ast }{\Sigma }_c$ channel we found three possible candidates for the $P_c^{+}(4450)$ with $J^P={\frac{1}{2}}^{-}$, ${\frac{3}{2}}^{-}$ and ${\frac{3}{2}}^{+}$ with almost degenerated energies. The $X(4140)$ resonance appears as a cusp in the $J/\psi \varphi$ channel due to the near coincidence of the $D_s^{\pm }{D}_s^{\ast \pm }$ and $J/\psi \varphi$ mass thresholds. The remaining three $X(4274)$, $X(4500)$ and $X(4700)$ resonances appear as conventional charmonium states with quantum numbers $3^3{P}_1$, $4^3{P}_0$ and $5^3{P}_0$, respectively; and whose masses and widths are slightly modified due to their coupling with the corresponding closest meson-meson thresholds.

    hep-phhep-exhep-latnucl-thPoS(2016)·2 citations
14. 14*

    A remark on the mathematics of the seesaw mechanism

    Fabien Besnard🇫🇷

    To demonstrate that matrices of seesaw type lead to a hieararchy in the neutrino masses, i.e. that there is a large gap in the singular spectrum of these matrices, one generally uses an approximate block-diagonalization procedure. In this note we show that no approximation is required to prove this gap property if the Courant-Fisher-Weyl theorem is used instead. This simple observation might not be original, however it does not seem to show up in the literature. We also sketch the proof of additional inequalities for the singular values of matrices of seesaw type.

    hep-phhep-thmath-phmath.MPJ.Phys.Comm.(2018)·4 citations
15. 15*

    Higher order quark number fluctuations via imaginary chemical potentials in $N_f=2+1$ QCD

    Massimo D'Elia🇮🇹 · Giuseppe Gagliardi🇮🇹 · Francesco Sanfilippo🇬🇧

    We discuss analytic continuation as a tool to extract the cumulants of the quark number fluctuations in the strongly interacting medium from lattice QCD simulations at imaginary chemical potentials. The method is applied to $N_f=2+1$ QCD, discretized with stout improved staggered fermions, physical quark masses and the tree level Symanzik gauge action, exploring temperatures ranging from 135 up to 350 MeV and adopting mostly lattices with $N_t=8$ sites in the temporal direction. The method is based on a global fit of various cumulants as a function of the imaginary chemical potentials. We show that it is particularly convenient to consider cumulants up to order two, and that below $T_c$ the method can be advantageous, with respect to a direct Montecarlo sampling at $\mu =0$, for the determination of generalized susceptibilities of order four or higher, and especially for mixed susceptibilities, for which the gain is well above one order of magnitude. We provide cumulants up to order eight, which are then used to discuss the radius of convergence of the Taylor expansion and the possible location of the second order critical point at real $\mu$: no evidence for such a point is found in the explored range of $T$ and for chemical potentials within present determinations of the pseudo-critical line.

    ↳ hep-lathep-phhep-thPRD(2017)·119 citations
16. 16*

    Study of lattice QCD at finite baryon density using the canonical approach

    V. G. Bornyakov🇷🇺 · D. L. Boyda🇷🇺 · V. A. Goy🇷🇺 · A. V. Molochkov🇷🇺 · Atsushi Nakamura🇷🇺 · A. A. Nikolaev🇷🇺 · V. I. Zakharov🇷🇺

    At finite baryon density lattice QCD first-principle calculations can not be performed due to the sign problem. In order to circumvent this problem, we use the canonical approach, which provides reliable analytical continuation from the imaginary chemical potential region to the real chemical potential region. We briefly present the canonical partition function method, describe our formulation, and show the results, obtained for two temperatures: $T/T_c=0.93$ and $T/T_c=0.99$ in lattice QCD with two flavors of improved Wilson fermions.

    ↳ hep-lathep-phEPJ Web Conf.(2017)·0 citations
17. 17*

    On the PeV knee of cosmic rays spectrum and TeV cutoff of electron spectrum

    Chao Jin🇨🇳 · Wei Liu🇨🇳 · Hong-Bo Hu🇨🇳 · Yi-Qing Guo🇨🇳

    Spectra of Cosmic Rays (CRs), particularly their features, may hold essential information about astroparticle and fundamental physics. Realizing that both $4$ PeV CR knee and electron's TeV break have nearly identical Lorentz factor, i.e. $\gamma \sim 10^6$, we propose that both CR nuclei and electron experience a threshold interaction with unknown light particle $\mathrm{X}$, widespread in the diffusive halo. The interaction occurs only when the Lorentz factor of CRs is larger than $10^6$. Via this process, the energy spectrum of each component has deformation above the threshold Lorentz factor, so both knee and spectral break of electrons can be naturally reproduced. Given the large uncertainties of the available measurements and simplified assumption, our model accommodates a wide mass range of the particle X, which is allowable from ultralight value to $\sim 1$ eV.

    ↳ astro-ph.HEastro-ph.GAhep-phPRD(2018)·11 citations
18. 18*

    Extracting kinetic freeze-out temperature and radial flow velocity from an improved Tsallis distribution

    Hai-Ling Lao🇨🇳 · Fu-Hu Liu🇨🇳 · Roy A. Lacey🇺🇸

    We analyze the transverse momentum ($p_T$) spectra of identified particles (${\pi }^{\pm }$, $K^{\pm }$, $p$, and $\bar{p}$) produced in gold-gold (Au-Au) and lead-lead (Pb-Pb) collisions over a $\sqrt{s_{NN}}$ (center-of-mass energy per nucleon pair) range from 14.5 GeV [one of the Relativistic Heavy Ion Collider (RHIC) energies] to 2.76 TeV [one of the Large Hadron Collider (LHC) energies]. For the spectra with a narrow $p_T$ range, an improved Tsallis distribution which is in fact the Tsallis distribution with radial flow is used. For the spectra with a wide $p_T$ range, a superposition of the improved Tsallis distribution and an inverse power-law is used. Both the extracted kinetic freeze-out temperature ($T_0$) and radial flow velocity (${\beta }_T$) increase with the increase of $\sqrt{s_{NN}}$, which indicates a higher excitation and larger expansion of the interesting system at the LHC. Both the values of $T_0$ and ${\beta }_T$ in central collisions are slightly larger than those in peripheral collisions, and they are independent of isospin and slightly dependent on mass.

    ↳ nucl-thhep-exhep-phnucl-exEPJA(2017)·51 citations
19. 19*

    Constraining Logotropic Unified Dark Energy Models

    V. M. C. Ferreira🇵🇹 · P. P. Avelino🇵🇹

    A unification of dark matter and dark energy in terms of a logotropic perfect dark fluid has recently been proposed, where deviations with respect to the standard $\Lambda \mathrm{CDM}$ model are dependent on a single parameter $B$. In this paper we show that the requirement that the linear growth of cosmic structures on comoving scales larger than $8h^{-1}\mathrm{Mpc}$ is not significantly affected with respect to the standard $\Lambda \mathrm{CDM}$ result provides the strongest constraint to date on the model ($B<6\times 10^{-7}$), an improvement of more than three orders of magnitude over previous constraints on the value of $B$. We further show that this constraint rules out the logotropic Unified Dark Energy model as a possible solution to the small scale problems of the $\Lambda$CDM model, including the cusp problem of Dark Matter halos or the missing satellite problem, as well as the original version of the model where the Planck energy density was taken as one of the two parameters characterizing the logotropic dark fluid.

    ↳ astro-ph.COgr-qchep-phhep-thPLB(2017)·18 citations
20. 20*

    A Mellin space approach to the conformal bootstrap

    Rajesh Gopakumar🇮🇳 · Apratim Kaviraj🇮🇳 · Kallol Sen🇯🇵 · Aninda Sinha🇮🇳

    We describe in more detail our approach to the conformal bootstrap which uses the Mellin representation of $CF{T}_d$ four point functions and expands them in terms of crossing symmetric combinations of $Ad{S}_{d+1}$ Witten exchange functions. We consider arbitrary external scalar operators and set up the conditions for consistency with the operator product expansion. Namely, we demand cancellation of spurious powers (of the cross ratios, in position space) which translate into spurious poles in Mellin space. We discuss two contexts in which we can immediately apply this method by imposing the simplest set of constraint equations. The first is the epsilon expansion. We mostly focus on the Wilson-Fisher fixed point as studied in an epsilon expansion about $d=4$. We reproduce Feynman diagram results for operator dimensions to $O({ϵ}^3)$ rather straightforwardly. This approach also yields new analytic predictions for OPE coefficients to the same order which fit nicely with recent numerical estimates for the Ising model (at $ϵ=1$). We will also mention some leading order results for scalar theories near three and six dimensions. The second context is a large spin expansion, in any dimension, where we are able to reproduce and go a bit beyond some of the results recently obtained using the (double) light cone expansion. We also have a preliminary discussion about numerical implementation of the above bootstrap scheme in the absence of a small parameter.

    ↳ hep-thcond-mat.stat-mechcond-mat.str-elhep-phJHEP(2017)·194 citations
21. 21*

    Numerical simulations of necklaces in SU(2) gauge-Higgs field theory

    Mark Hindmarsh🇫🇮 · Kari Rummukainen🇫🇮 · David J. Weir🇫🇮

    We perform the first numerical simulations of necklaces in a non-Abelian gauge theory. Necklaces are composite classical solutions which can be interpreted as monopoles trapped on strings, rather generic structures in a Grand Unified Theory. We generate necklaces from random initial conditions, modelling a phase transition in the early Universe, and study the evolution. For all cases, we find that the necklace system shows scaling behaviour similar to that of a network of ordinary cosmic strings. Furthermore, our simulations indicate that comoving distance between the monopoles or semipoles along the string asymptotes to a constant value at late times. This means that while the monopole-to-string energy density ratio decreases as the inverse of the scale factor, a horizon-size length of string has a large number of monopoles, significantly affecting the dynamics of string loops. We argue that gravitational wave bounds from millisecond pulsar timing on the string tension in the Nambu-Goto scenario are greatly relaxed.

    ↳ astro-ph.COhep-phhep-thPRD(2017)·23 citations
22. 22*

    Leading order relativistic chiral nucleon-nucleon interaction

    Xiu-Lei Ren🇨🇳 · Kai-Wen Li🇨🇳 · Li-Sheng Geng🇨🇳 · Bing-Wei Long🇨🇳 · Peter Ring🇨🇳 · Jie Meng🇨🇳

    Motivated by the successes of relativistic theories in studies of atomic/molecular and nuclear systems and the need for a relativistic chiral force in relativistic nuclear structure studies, we explore a new relativistic scheme to construct the nucleon-nucleon interaction in the framework of covariant chiral effective field theory. The chiral interaction is formulated up to leading order with covariant power counting and a Lorentz invariant chiral Lagrangian. We find that the relativistic scheme induces all six spin operators needed to describe the nuclear force. A detailed investigation of the partial wave potentials shows a better description of the ${}^1{S}_0$ and ${}^3{P}_0$ phase shifts than the leading order Weinberg approach, and similar to that of the next-to-leading order Weinberg approach. For the other partial waves with angular momenta $J\ge 1$, the relativistic results are almost the same as their leading order non-relativistic counterparts.

    ↳ nucl-thhep-phCPC(2018)·90 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.