Fri·Mar 23, 2018Friday·March 23, 2018

1. 01*

   Jet Charge and Machine Learning

   Katherine Fraser🇺🇸 · Matthew D. Schwartz🇺🇸

   Modern machine learning techniques, such as convolutional, recurrent and recursive neural networks, have shown promise for jet substructure at the Large Hadron Collider. For example, they have demonstrated effectiveness at boosted top or W boson identification or for quark/gluon discrimination. We explore these methods for the purpose of classifying jets according to their electric charge. We find that both neural networks that incorporate distance within the jet as an input and boosted decision trees including radial distance information can provide significant improvement in jet charge extraction over current methods. Specifically, convolutional, recurrent, and recursive networks can provide the largest improvement over traditional methods, in part by effectively utilizing distance within the jet or clustering history. The advantages of using a fixed-size input representation (as with the CNN) or a small input representation (as with the RNN) suggest that both convolutional and recurrent networks will be essential to the future of modern machine learning at colliders.

   hep-phstat.MLJHEP(2018)·94 citations
2. 02*

   Neutron stars with spin polarized self-interacting dark matter

   Zeinab Rezaei🇮🇷

   Dark matter, one of the important portion of the universe, could affect the visible matter in neutron stars. An important physical feature of dark matter is due to the spin of dark matter particles. Here, applying the piecewise polytropic equation of state for the neutron star matter and the equation of state of spin polarized self-interacting dark matter, we investigate the structure of neutron stars which are influenced by the spin polarized self-interacting dark matter. The behavior of the neutron star matter and dark matter portions for the stars with different values of the interaction between dark matter particles and spin polarization of dark matter is considered. In addition, we present the value of the gravitational redshift of these stars in different cases of spin polarized and self-interacting dark matter.

   hep-phastro-ph.HEastro-ph.SRAstropart.Phys.(2018)·8 citations
3. 03*

   A flavoured dark sector

   Sophie Renner🇩🇪 · Pedro Schwaller🇩🇪

   We explore the phenomenology of a QCD-like dark sector which confines around the GeV scale. The dark sector inherits a flavour structure from a coupling between dark quarks and SM quarks via a heavy mediator, which leads to exciting new phenomena. While stable baryonic bound states are the dark matter candidates, the phenomenology is dominated by the lightest composite mesons, the dark pions, which can have decay lengths ranging from millimetres to hundreds of meters. For masses below 1.5 GeV, their exclusive decays to SM mesons are calculated for the first time by matching both dark and visible sectors to a chiral Lagrangian. Constraints from big bang nucleosynthesis, dark matter direct detection and flavour single out a small region of allowed parameter space for dark pion masses below 5 GeV. It is best probed by the fixed target experiments NA62 and SHiP, where dark pions can be produced copiously in rare decays like B to K piD. Heavier dark pions are best searched for at the LHC, where they decay after hadronisation to produce jets which emerge into SM states within the detector. Here the flavour structure ensures different flavours emerge on different length scales, leading to a striking new feature in the emerging jets signature.

   hep-phhep-exJHEP(2018)·76 citations
4. 04*

   Pseudoscalar pole light-by-light contributions to the muon $(g-2)$ in Resonance Chiral Theory

   A. Guevara🇪🇸 · P. Roig🇲🇽 · J. J. Sanz-Cillero🇪🇸

   We have studied the $P\to {\gamma }^{\star }{\gamma }^{\star }$ transition form-factors ($P={\pi }^0,\eta ,{\eta }^{\prime }$) within a chiral invariant framework that allows us to relate the three form-factors and evaluate the corresponding contributions to the muon anomalous magnetic moment $a_{\mu }$, through pseudoscalar pole contributions. We use a chiral invariant Lagrangian to describe the interactions between the pseudo-Goldstones from the spontaneous chiral symmetry breaking and the massive meson resonances. We will consider just the lightest vector and pseudoscalar resonance multiplets. Photon interactions and flavor breaking effects are accounted for in this covariant framework. This article studies the most general corrections of order $m_P^2$ within this setting. Requiring short-distance constraints fixes most of the parameters entering the form-factors, consistent with previous determinations. The remaining ones are obtained from a fit of these form-factors to experimental measurements in the space-like ($q^2\le 0$) region of photon momenta. The combination of data, chiral symmetry relations between form-factors and high-energy constraints allows us to determine with improved precision the on-shell $P$-pole contribution to the Hadronic Light-by-Light scattering of the muon anomalous magnetic moment: we obtain $a_{\mu }^{P,HLbL}=(8.47\pm 0.16)\cdot 10^{-10}$ for our best fit. This result was obtained excluding BaBar ${\pi }^0$ data, which our analysis finds in conflict with the remaining experimental inputs. This study also allows us to determine the parameters describing the $\eta -{\eta }^{\prime }$ system in the two-mixing angle scheme and their correlations. Finally, a preliminary rough estimate of the impact of loop corrections ($1/N_C$) and higher vector multiplets (asym) enlarges the uncertainty up to $a_{\mu }^{P,HLbL}=(8.47\pm 0.16_{\mathrm{sta}}\pm 0.09_{1/N_C}{}_{-0.0}^{+0.5}{}_{\mathrm{asym}})\cdot 10^{-10}$.

   hep-phJHEP(2018)·68 citations
5. 05*

   The Linear BESS Model at the LHC

   Jose Urbina🇨🇱 · Alfonso R. Zerwekh🇨🇱

   In this work we consider the Linear BESS model at the LHC. This model can be seen as an adequate benchmark for exploring the phenomenological consequences of a composite Higgs sector since its particle content is the one we would expect in a realistic low energy description of modern (Technicolor inspired) dynamical electroweak symmetry breaking scenarios. Additionally, the model exhibits the property of decoupling, producing a good ultraviolet behavior. We focus on the limits on the masses of the new heavy vector particles imposed by direct resonance searches, recent measurements of the decay of the Higgs boson into two photons and the electroweak precision tests. We found that the model is capable to accommodate the existing experimental constrains provided that the spin-1 resonances are heavier than 3.4 TeV.

   hep-phhep-exNPB(2018)·2 citations
6. 06*

   Implications of Higgs Discovery for the Strong CP Problem and Unification

   Lawrence J. Hall🇺🇸 · Keisuke Harigaya🇺🇸

   A $Z_2$ symmetry that extends the weak interaction, $SU(2{)}_L\to SU(2{)}_L\times SU(2{)}^{\prime }$, and the Higgs sector, $H(2)\to H(2,1)+H^{\prime }(1,2)$, yields a Standard Model quartic coupling that vanishes at scale $v^{\prime }=<H^{\prime }>\gg <H>$. Near $v^{\prime }$, theories either have a "prime" sector, or possess "Left-Right" (LR) symmetry with $SU(2{)}^{\prime }=SU(2{)}_R$. If the $Z_2$ symmetry incorporates spacetime parity, these theories can solve the strong CP problem. The LR theories have all quark and lepton masses arising from operators of dimension 5 or more, requiring Froggatt-Nielsen structures. Two-loop contributions to $\bar{\theta }$ are estimated and typically lead to a neutron electric dipole moment of order $10^{-27}$e cm that can be observed in future experiments. Minimal models, with gauge group $SU(3)\times SU(2{)}_L\times SU(2{)}_L\times U(1{)}_{B-L}$, have precise gauge coupling unification for $v^{\prime }=10^{10\pm 1}$ GeV, successfully correlating gauge unification with the observed Higgs mass of $125$ GeV. With $SU(3)\times U(1{)}_{B-L}$ embedded in $SU(4)$, the central value of the unification scale is reduced from $10^{16-17}$ GeV to below $10^{16}$ GeV, improving the likelihood of proton decay discovery. Unified theories based on $SO(10)\times CP$ are constructed that have $H+H^{\prime }$ in a $16$ or $144$ and generate higher-dimensional flavor operators, while maintaining perturbative gauge couplings.

   hep-phJHEP(2018)·80 citations
7. 07*

   Mapping The Neutrino Floor For Dark Matter-Electron Direct Detection Experiments

   Jason Wyenberg🇺🇸 · Ian M. Shoemaker🇺🇸

   We study the discovery reach of future Dark Matter (DM) Direct Detection experiments using DM-electron scattering in the presence of the solar neutrino background. At these low energies traditional methods for nuclear and electronic recoil discrimination fail, implying that the neutrino-{\it nucleus} scattering background can be sizable. We calculate discovery limits based on ionization values of signal and background, and quantify the dependence on the ionization model. Moreover, we explore how the dependence of the DM cross section discovery limits vary with exposure, electronic/nuclear recoil discrimination, DM form factors, and DM astrophysical uncertainties.

   hep-phPRD(2018)·34 citations
8. 08*

   The radio telescope search for the resonant conversion of cold dark matter axions from the magnetized astrophysical sources

   Fa Peng Huang🇰🇷 · Kenji Kadota🇰🇷 · Toyokazu Sekiguchi🇯🇵 · Hiroyuki Tashiro🇯🇵

   We study the conditions for the adiabatic resonant conversion of the cold dark matter (CDM) axions into photons in existence of the astrophysically sourced strong magnetic fields such as those in the neutron star magnetosphere. We demonstrate the possibility that the forthcoming radio telescopes such as the SKA (Square Kilometre Array) can probe those photon signals from the CDM axions.

   hep-phastro-ph.COastro-ph.HEPRD(2018)·143 citations
9. 09*

   Normal hierarchy neutrino mass model revisited with leptogenesis

   Ananya Mukherjee🇮🇳 · Mrinal Kumar Das🇮🇳 · Jayanta Kumar Sarma🇮🇳

   We have studied the scenario of baryogenesis via leptogenesis in an $A_4$ flavor symmetric framework considering type I seesaw as the origin of neutrino mass. Because of the presence of the fifth generation right handed neutrino the model naturally generates non-zero reactor mixing angle. We have considered two vev alignments for the extra flavon $\eta$ and studied the consequences in detail. As a whole the additional flavon along with the extra right handed neutrinos allow us to study thermal leptogenesis by the decay of the lightest right handed neutrino present in the model. We have computed the matter-antimatter asymmetry for both flavor dependent and flavor independent leptogenesis by considering a considerably wider range of right handed neutrino mass. Finally, we correlate the baryon asymmetry of the universe (BAU) with the model parameters and light neutrino masses.

   hep-ph2 citations
10. 10*

    Energy and Centrality Dependent Study of Deconfinement Phase Transition in a Color String Percolation Approach at RHIC Energies

    Pragati Sahoo🇮🇳 · Sudipan De🇮🇳 · Swatantra Kumar Tiwari🇮🇳 · Raghunath Sahoo🇮🇳

    We take the experimental data for transverse momentum spectra of identified charged hadrons in different centrality classes for nucleus-nucleus (A+A) collisions at various Relativistic Heavy-Ion Collider (RHIC) energies measured by the STAR collaboration. We analyse these data in the framework of color string percolation model (CSPM) in order to extract various percolation parameters at different centralities at RHIC energies to study the effect of collision geometry and collision energy. We use these parameters to study the centrality dependent behaviour of initial temperature of the percolation cluster, energy density, average transverse momentum, shear viscosity to entropy density ratio ($\eta /s$) and trace anomaly for different energies at RHIC from $\sqrt{s_{\mathrm{NN}}}$ = 19.6 to 200 GeV. These observables are found to strongly depend on centrality at various collision energies. The critical percolation density, which is related to the deconfinement phase transition is achieved in the most central nucleus-nucleus collisions, while it fails in the peripheral collisions. A universal scaling is observed in color suppression factor and initial temperatures when studied as a function of charged particle pseudorapidity distribution scaled by nuclear overlap area at RHIC energies. The minimum of $\eta /s$ is observed in the most central collisions at $\sqrt{s_{\mathrm{NN}}}$ = 130 and 200 GeV.

    hep-phhep-exnucl-exnucl-thEPJA(2018)·39 citations
11. 11*

    Spin polarized phases in strongly interacting matter: interplay between axial-vector and tensor mean fields

    Tomoyuki Maruyama🇯🇵 · Eiji Nakano🇯🇵 · Kota Yanase🇯🇵 · Naotaka Yoshinaga🇯🇵

    The spontaneous spin polarization of strongly interacting matter due to axial-vector and tensor type interactions is studied at zero temperature and high baryon-number densities. We start with the mean-field Lagrangian for the axial-vector and tensor interaction channels, and find in the chiral limit that the spin polarization due to the tensor mean field ($U$) takes place first as the density increases for sufficiently strong coupling constants, and then that due to the axial-vector mean field ($A$) emerges in the region of finite tensor mean field. This can be understood that making the axial-vector mean field finite requires a broken chiral symmetry somehow, which is achieved by the finite tensor mean field in the present case. It is also found from symmetry argument that there appear the type I (II) Nambu-Goldstone modes with a linear (quadratic) dispersion in the spin polarized phase with $U\ne 0$ and $A=0$ ($U\ne 0$ and $A\ne 0$), although these two phases exhibit the same symmetry breaking pattern.

    hep-phnucl-thPRD(2018)·8 citations
12. 12*

    $D\bar{D}$ asymmetry at low and high energies and possible consequences for prompt atmospheric neutrinos

    Antoni Szczurek🇵🇱 · Rafal Maciula🇵🇱

    We discuss the role of unfavoured light quark/antiquark to $D$ meson fragmentation. The unknown parameters of fragmentation process are adjusted to describe the asymmetry for $D^{+}$ and $D^{-}$ production measured by the LHCb. Predictions for similar asymmetry for neutral $D$ mesons are presented. The predicted asymmetry at large rapidity (or $x_F$) are very large which is related to the valence-quark contribution. As a result, prompt atmospheric neutrino flux at high neutrino energies can be much larger than for the conventional $c\to D$ fragmentation. We predict large rapidity-dependent $D^{+}/D^{-}$ and $D^0/{\bar{D}}^0$ asymmetries for low ($\sqrt{s}=$ 20 - 100 GeV) energies. The $q/\bar{q}\to D$ fragmentation leads to enhanced production of $D$ mesons at low energies. Predictions for fixed target $p{+}^4\text{He}$ collisions relevant for a fixed target LHCb experiment are discussed.

    hep-phhep-exActa Phys.Polon.B(2018)·0 citations
13. 13*

    Angular Momentum Sum Rule Violation in QCD Due to Confinement and The Proton Spin Crisis

    Gouranga C Nayak🇺🇸

    The proton spin crisis remains an unsolved problem in physics. In this paper we find that due to the confinement of partons inside the hadron the angular momentum sum rule in QCD is violated. Hence we find that the non-vanishing angular momentum flux contribution of the partons in QCD should be added to the spin and angular momentum of the partons to solve the proton spin crisis.

    hep-phhep-latnucl-th5 citations
14. 14*

    Geometrical scaling description for the exclusive production of vector mesons and deeply virtual Compton scattering

    Felipe G. Ben🇧🇷 · Magno V. T. Machado🇧🇷 · Werner K. Sauter🇧🇷

    In this work, we investigate the exclusive production of particles in scattering processes in the so-called saturation region. Within this scheme the phenomenon of geometric scaling takes place: cross sections are functions only of a dimensionless combination of the relevant kinematic variables, which happens both in inclusive and diffractive cases, as in the production of vector mesons. In particular, the scaling variable is given in general by $\tau =Q^2/Q_s^2$, where $Q^2$ is the photon virtuality and $Q_s$ represents the saturation scale, which drives the energy dependence and the corresponding nuclear effects. Based on the scaling property, we are able to derive a universal expression for the cross sections for the exclusive vector meson production and deeply virtual Compton scattering (DVCS) in both photon-proton and photon-nucleus interactions. This phenomenological result describes all available data from DESY-HERA for $\rho$, $\varphi$ and $J/\psi$ production and DVCS measurements. A discussion is also carried out on the size of nuclear shadowing corrections on photon-nucleus interaction.

    hep-ph1 citation
15. 15*

    Particle physics origin of the 5 MeV bump in the reactor antineutrino spectrum?

    Jeffrey M. Berryman🇺🇸 · Vedran Brdar🇩🇪 · Patrick Huber🇺🇸

    One of the most puzzling questions in neutrino physics is the origin of the excess at 5 MeV in the reactor antineutrino spectrum. In this paper, we explore the excess via the reaction ${}^{13}$C$(\overline{\nu },{\overline{\nu }}^{\prime }n{)}^{12}$C${}^{\ast }$ in organic scintillator detectors. The de-excitation of ${}^{12}$C${}^{\ast }$ yields a prompt $4.4$ MeV photon, while the thermalization of the product neutron causes proton recoils, which in turn yield an additional prompt energy contribution with finite width. Together, these effects can mimic an inverse beta decay event with around 5 MeV energy. We consider several non-standard neutrino interactions to produce such a process and find that the parameter space preferred by Daya Bay is disfavored by measurements of neutrino-induced deuteron disintegration and coherent elastic neutrino-nucleus scattering. While non-minimal particle physics scenarios may be viable, a nuclear physics solution to this anomaly appears more appealing.

    hep-phhep-exnucl-exnucl-thPRD(2019)·40 citations
16. 16*

    Crawling technicolor

    O. Catà🇩🇪 · R.J. Crewther🇦🇺 · Lewis C. Tunstall🇨🇭

    We analyze the Callan-Symanzik equations when scale invariance at a nontrivial infrared (IR) fixed point ${\alpha }_{\mathrm{IR}}^{}$ is realized in the Nambu-Goldstone (NG) mode. As a result, Green's functions at ${\alpha }_{\mathrm{IR}}^{}$ do not scale in the same way as for the conventional Wigner-Weyl (WW) mode. This allows us to propose a new mechanism for dynamical electroweak symmetry breaking where the running coupling $\alpha$ "crawls" towards (but does not pass) ${\alpha }_{\mathrm{IR}}^{}$ in the exact IR limit. The NG mechanism at ${\alpha }_{\mathrm{IR}}^{}$ implies the existence of a massless dilaton $\sigma$, which becomes massive for IR expansions in $ϵ\equiv {\alpha }_{\mathrm{IR}}^{}-\alpha$ and is identified with the Higgs boson. Unlike "dilatons" that are close to a WW-mode fixed point or associated with a Coleman-Weinberg potential, our NG-mode dilaton is genuine and hence naturally light. Its (mass)${}^2$ is proportional to $ϵ{\beta }^{\prime }(4+{\beta }^{\prime })F_{\sigma }^{-2}⟨{\hat{G}}^2{⟩}_{\text{vac}}$, where ${\beta }^{\prime }$ is the (positive) slope of the beta function at ${\alpha }_{\mathrm{IR}}^{}$, $F_{\sigma }$ is the dilaton decay constant and $⟨{\hat{G}}^2{⟩}_{\text{vac}}$ is the technigluon condensate. Our effective field theory for this works because it respects Zumino's consistency condition for dilaton Lagrangians. We find a closed form of the Higgs potential with ${\beta }^{\prime }$-dependent deviations from that of the Standard Model. Flavor-changing neutral currents are suppressed if the crawling region $\alpha \lesssim {\alpha }_{\mathrm{IR}}^{}$ includes a sufficiently large range of energies above the TeV scale. In Appendix A, we observe that, contrary to folklore, condensates protect fields from decoupling in the IR limit.

    hep-phhep-lathep-thPRD(2019)·61 citations
17. 17*

    Chiral and $U(1{)}_A$ restoration for the scalar/pseudoscalar meson nonets

    A. Gómez Nicola🇪🇸 · J. Ruiz de Elvira🇨🇭

    We analyze the restoration pattern of the members of the scalar and pseudoscalar meson nonets under chiral $O(4)$ and $U(1{)}_A$ symmetries. For that purpose, we exploit QCD Ward Identities (WI), which allow one to relate susceptibilities with quark condensates, as well as susceptibility differences with meson vertices. In addition, we consider the low-energy realization of QCD provided by $U(3)$ Chiral Perturbation Theory (ChPT) at finite temperature to perform a full analysis of the different correlators involved. Our analysis suggests $U(1{)}_A$ partner restoration if chiral symmetry partners are also degenerated. This is also confirmed by the ChPT analysis when the light chiral limit is reached. Partner degeneration for the $I=1/2$ sector, the behavior of $I=0$ mixing and the temperature scaling of meson masses predicted by WI are also studied. Special attention is paid to the connection of our results with recent lattice analyses.

    hep-phhep-latnucl-thPRD(2018)·38 citations
18. 18*

    Universal Formula for Baryon Spectra in Heavy-ion Collisions and its Implications

    Rudolph C. Hwa🇺🇸 · Lilin Zhu🇨🇳

    In an unconventional presentation of the data on the transverse momentum spectra of baryons produced in heavy-ion collisions, regularities are found that make possible the discovery of a universal formula valid for $p,\Lambda ,\Xi$ and $\Omega$. The formula describes the baryon distributions over wide ranges of $p_T(0.5{}_{\sim }^{<}{p}_T{}_{\sim }^{<}5$ GeV/c) for $0.06{}_{\sim }^{<}\sqrt{s_{NN}}{}_{\sim }^{<}3$ TeV, except for very peripheral collisions. Some aspects of their empirical properties are derived in the recombination model, resulting in a revelation of some features of the light and strange quark distributions before hadronization. Interpretation of the inverse slopes of their exponential behavior leads to an implication that cannot accommodate the conventional description of fluid flow. This is mainly a study of phenomenology without detailed model input.

    ↳ nucl-exhep-phnucl-thPRC(2018)·10 citations
19. 19*

    Inflation with Planck: a survey of some "exotic" inflationary models

    Cláudio Gomes🇵🇹 · Orfeu Bertolami🇵🇹 · João G. Rosa🇵🇹

    We examine some inflationary models based on modifications of gravity in the light of Planck 2015 data, such as the generalised Chaplygin inspired inflation, models based in $N=1$ supergravity and braneworld scenarios. We also show that, conversely, potentials with a very flat plateau yield a primordial spectrum similar to that of the Starobinsky model with no need to modify general relativity.

    ↳ hep-thgr-qchep-phPRD(2018)·19 citations
20. 20*

    Superconformal Subcritical Hybrid Inflation

    Koji Ishiwata🇯🇵

    We consider D-term hybrid inflation in the framework of superconformal supergravity. In part of the parameter space, inflation continues for subcritical inflaton field value. Consequently, a new type of inflation emerges, which gives predictions for the scalar spectral index and the tensor-to-scalar ratio that are consistent with the Planck 2015 results. The potential in the subcritical regime is found to have a similar structure to one in the simplest class of superconformal alpha attractors.

    ↳ astro-ph.COhep-phhep-thPLB(2018)·12 citations
21. 21*

    Derivation of spontaneously broken gauge symmetry from the consistency of effective field theory I: Massive vector bosons coupled to a scalar field

    D. Djukanovic🇩🇪 · J. Gegelia🇩🇪 · Ulf-G. Meißner🇩🇪

    We revisit the problem of deriving local gauge invariance with spontaneous symmetry breaking in the context of an effective field theory. Previous derivations were based on the condition of tree-order unitarity. However, the modern point of view considers the Standard Model as the leading order approximation to an effective field theory. As tree-order unitarity is in any case violated by higher-order terms in an effective field theory, it is instructive to investigate a formalism which can be also applied to analyze higher-order interactions. In the current work we consider an effective field theory of massive vector bosons interacting with a massive scalar field. We impose the conditions of generating the right number of constraints for systems with spin-one particles and perturbative renormalizability as well as the separation of scales at one-loop order. We find that the above conditions impose severe restrictions on the coupling constants of the interaction terms. Except for the strengths of the self-interactions of the scalar field, that can not be determined at this order from the analysis of three- and four-point functions, we recover the gauge-invariant Lagrangian with spontaneous symmetry breaking taken in the unitary gauge as the leading order approximation to an effective field theory. We also outline the additional work that is required to finish this program.

    ↳ hep-thhep-lathep-phnucl-thPLB(2018)·4 citations
22. 22*

    Quenches near Ising quantum criticality as a challenge for artificial neural networks

    Stefanie Czischek🇩🇪 · Martin Gärttner🇩🇪 · Thomas Gasenzer🇩🇪

    The near-critical unitary dynamics of quantum Ising spin chains in transversal and longitudinal magnetic fields is studied using an artificial neural network representation of the wave function. A focus is set on strong spatial correlations which build up in the system following a quench into the vicinity of the quantum critical point. We compare correlations observed following reinforcement learning of the network states with analytical solutions in integrable cases and tDMRG simulations, as well as with predictions from a semi-classical discrete Truncated Wigner analysis. While the semi-classical approach excells mainly at short times and for small transverse fields, the neural-network representation provides accurate results for a much wider range of parameters. Where long-range spin-spin correlations build up in the long-time dynamics we find qualitative agreement with exact results while quantitative deviations are of similar size as for the semi-classically predicted correlations, and slow convergence is observed when increasing the number of hidden neurons.

    ↳ quant-phcond-mat.dis-nnhep-phPRB(2018)·66 citations
23. 23*

    Reweighting Lefschetz Thimbles

    Stefan Bluecher🇩🇪 · Jan M. Pawlowski🇩🇪 · Manuel Scherzer🇩🇪 · Mike Schlosser🇩🇪 · Ion-Olimpiu Stamatescu🇩🇪 · Sebastian Syrkowski🇩🇪 · Felix P.G. Ziegler🇩🇪

    One of the main challenges in simulations on Lefschetz thimbles is the computation of the relative weights of contributing thimbles. In this paper we propose a solution to that problem by means of computing those weights using a reweighting procedure. Besides we present recipes for finding parametrizations of thimbles and anti-thimbles for a given theory. Moreover, we study some approaches to combine the Lefschetz thimble method with the Complex Langevin evolution. Our numerical investigations are carried out by using toy models among which we consider a one-site z^4 model as well as a U(1) one-link model.

    ↳ hep-lathep-phhep-thSciPost Phys.(2018)·35 citations
24. 24*

    Confinement and XSB in QCD: Mysteries and beauty of soliton dynamics in nonAbelian gauge theories

    Kenichi Konishi🇮🇹

    Deep insights into the possible infrared dynamics of strongly-coupled nonAbelian gauge theories such as QCD come from the analyses of $\mathcal{N}=1$ or $\mathcal{N}=2$ supersymmetric gauge theories. Central in the whole discussion will be the topological soliton monopoles and vortices and their quantum dynamics. We review the arguments that nonAbelian monopoles, free from the classic "difficulties", can be defined semi-classically via the topology and stability connection to the better understood nonAbelian vortices. Recent results on $C{P}^{N-1}$ models on $2D$ worldsheet of finite width, establish the quantum mechanical nature of such nonAbelian monopoles. An interesting class of RG flows and emergence of confining vacua "nearby" strongly-coupled infrared-fixed point (IRFP) conformal theories are discussed in the context of most singular vacua in $\mathcal{N}=2$ supersymmetric QCD. Certain analogy with the real-world QCD is drawn. In many systems, color-flavor locking emerges as a crucial mechanism for the gauge system to avoid dynamical Abelianization.

    ↳ hep-thhep-lathep-ph2 citations
25. 25*

    AdS-phobia, the WGC, the Standard Model and Supersymmetry

    Eduardo Gonzalo🇪🇸 · Alvaro Herráez🇪🇸 · Luis E. Ibáñez🇪🇸

    It has been recently argued that an embedding of the SM into a consistent theory of quantum gravity may imply important constraints on the mass of the lightest neutrino and the cosmological constant ${\Lambda }_4$. The constraints come from imposing the absence of any non-SUSY AdS stable vacua obtained from any consistent compactification of the SM to 3 or 2 dimensions. This condition comes as a corollary of a recent extension of the Weak Gravity Conjecture (WGC) by Ooguri and Vafa. In this paper we study $T^2/Z_N$ compactifications of the SM to two dimensions in which SM Wilson lines are projected out, leading to a considerable simplification. We analyze in detail a $T^2/Z_4$ compactification of the SM in which both complex structure and Wilson line scalars are fixed and the potential is only a function of the area of the torus $a^2$. We find that the SM is not robust against the appearance of AdS vacua in 2D and hence would be by itself inconsistent with quantum gravity. On the contrary, if the SM is embedded at some scale $M_{SS}$ into a SUSY version like the MSSM, the AdS vacua present in the non-SUSY case disappear or become unstable. This means that WGC arguments favor a SUSY version of the SM, independently of the usual hierarchy problem arguments. In a $T^2/Z_4$ compactification in which the orbifold action is embedded into the $B-L$ symmetry the bounds on neutrino masses and the cosmological constant are recovered. This suggests that the MSSM should be extended with a $U(1{)}_{B-L}$ gauge group. In other families of vacua the spectrum of SUSY particles is further constrained in order to avoid the appearance of new AdS vacua or instabilities. We discuss a possible understanding of the little hierarchy problem in this context.

    ↳ hep-thhep-phJHEP(2018)·42 citations
26. 26*

    All rational one-loop Einstein-Yang-Mills amplitudes at four points

    Dhritiman Nandan🇬🇧 · Jan Plefka🇩🇪 · Gabriele Travaglini🇬🇧

    All four-point mixed gluon-graviton amplitudes in pure Einstein-Yang-Mills theory with at most one state of negative helicity are computed at one-loop order and maximal powers of the gauge coupling using D-dimensional generalized unitarity. The resulting purely rational expressions take very compact forms. We comment on the color-kinematics duality picture and a relation to collinear limits of pure gluon amplitudes.

    ↳ hep-thhep-phJHEP(2018)·23 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.