Fri·Dec 30, 2016Friday·December 30, 2016

1. 01*

   Kaluza-Klein Towers in the Early Universe: Phase Transitions, Relic Abundances, and Applications to Axion Cosmology

   Keith R. Dienes🇺🇸 · Jeff Kost🇺🇸 · Brooks Thomas🇺🇸

   We study the early-universe cosmology of a Kaluza-Klein (KK) tower of scalar fields in the presence of a mass-generating phase transition, focusing on the time-development of the total tower energy density (or relic abundance) as well as its distribution across the different KK modes. We find that both of these features are extremely sensitive to the details of the phase transition and can behave in a variety of ways significant for late-time cosmology. In particular, we find that the interplay between the temporal properties of the phase transition and the mixing it generates are responsible for both enhancements and suppressions in the late-time abundances, sometimes by many orders of magnitude. We map out the complete model parameter space and determine where traditional analytical approximations are valid and where they fail. In the latter cases we also provide new analytical approximations which successfully model our results. Finally, we apply this machinery to the example of an axion-like field in the bulk, mapping these phenomena over an enlarged axion parameter space that extends beyond those accessible to standard treatments. An important by-product of our analysis is the development of an alternate "UV-based" effective truncation of KK theories which has a number of interesting theoretical properties that distinguish it from the more traditional "IR-based" truncation typically used in the extra-dimension literature.

   hep-phastro-ph.COPRD(2017)·18 citations
2. 02*

   $\mathcal{C}\mathcal{P}$ violation with an unbroken $\mathcal{C}\mathcal{P}$ transformation

   Michael Ratz🇺🇸 · Andreas Trautner🇩🇪

   A $\mathcal{C}\mathcal{P}$ conserving $\mathrm{SU}(3)$ gauge theory is spontaneously broken to ${\mathrm{T}}_7$ by the vacuum expectation value (VEV) of a $15$-plet. Even though the $\mathrm{SU}(3)$-$\mathcal{C}\mathcal{P}$ transformation is not broken by the VEV, the theory exhibits physical $\mathcal{C}\mathcal{P}$ violation in the broken phase. This is because the $\mathrm{SU}(3)$-$\mathcal{C}\mathcal{P}$ transformation corresponds to the unique order-two outer automorphism of ${\mathrm{T}}_7$, which is not a physical $\mathcal{C}\mathcal{P}$ transformation for the ${\mathrm{T}}_7$ states, and there is no other possible $\mathcal{C}\mathcal{P}$ transformation. We explicitly demonstrate that $\mathcal{C}\mathcal{P}$ is violated by calculating a $\mathcal{C}\mathcal{P}$ odd decay asymmetry in the broken phase. This scenario provides us with a natural protection for topological vacuum terms, ensuring that $\theta G_{\mu \nu }{\tilde{G}}^{\mu \nu }$ is absent even though $\mathcal{C}\mathcal{P}$ is violated for the physical states of the model.

   hep-phhep-thJHEP(2017)·10 citations
3. 03*

   On the non-detection of Glashow resonance in IceCube

   Sarira Sahu🇲🇽 · Bing Zhang🇺🇸

   Electron anti-neutrinos at the Glashow resonance (GR, at $E_{{\bar{\nu }}_e}\sim 6.3$ PeV) have an enhanced probability to be detected. With three neutrinos detected by IceCube in the (1-2) PeV energy range at present, one would expect that about 1 to 4 GR ${\bar{\nu }}_e$ should have been detected. The high-energy $\sim 8.7$ PeV muon neutrino detected by IceCube may not be a GR event. If so, we expect to detect 50 to 70 GR ${\bar{\nu }}_e$, then one would have a "missing Glashow-resonance problem". This would suggest (1) that $p\gamma$ interaction rather than $pp$ interaction is the dominant channel to produce the observed IceCube high-energy neutrinos, (2) that multi-pion $p\gamma$ interactions are suppressed, and (3) that the magnetic field and photon energy density in the $p\gamma$ emission region is such that significant ${\mu }^{+}$ cooling occurs before decaying, yet ${\pi }^{+}$'s essentially do not cool before decaying.

   hep-phastro-ph.HEJHEAp(2018)·13 citations
4. 04*

   Effects Of leptonic non-unitarity on lepton flavor violation, neutrino oscillation, leptogenesis and lightest neutrino mass

   Gayatri Ghosh🇮🇳 · Kalpana Bora🇮🇳

   Neutrino Physics is a mature branch of science with all the three neutrino mixing angles and two mass squared differences determined with high precision. Inspite of several experimental verifications of neutrino oscillations and precise measurements of two mass squared differences and the three mixing angles, the unitarity of the leptonic mixing matrix is not yet established, leaving room for the presence of small non-unitarity effects. Deriving the bounds on these non-unitarity parameters from existing experimental constraints, on cLFV decays such as, $\mu \to e\gamma$, $\mu \to \tau \gamma$, $\tau \to e\gamma$, we study their effects on the generation of baryon asymmetry through leptogenesis and neutrino oscillation probabilities. We consider a model where see-saw is extended by an additional singlet $S$ which is very light, but can give rise to non-unitarity effects without affecting the form on see-saw formula. We do a parameter scan of a minimal see-saw model in a type I see-saw framework satisfying the Planck data on baryon to photon ratio of the Universe, which lies in the interval, $5.8\times 10^{-10}<Y_B<6.6\times 10^{-10}(BBN)$. We predict values of lightest neutrino mass, and Dirac and Majorana CP-violating phase ${\delta }_{CP}$, $\alpha$ and $\beta$, for normal hierarchy and inverted hierarchy for one flavor leptogenesis. It is worth mentioning that all these four quantities are unknown yet, and future experiments will be measuring them.

   hep-phAdv.High Energy Phys.(2018)·4 citations
5. 05*

   Analysis of right-handed Majorana neutrino mass in an $SU(4)\times SU(2{)}_L\times SU(2{)}_R$ Pati--Salam model with democratic texture

   Masaki J. S. Yang🇯🇵

   In this paper, we attempt to build an unified model with democratic texture, that have some unification between $Y_{\nu }$ and $Y_u$. Since the $S_{3L}\times S_{3R}$ flavor symmetry is chiral, the unified gauge group is assumed to be Pati-Salam type $SU(4{)}_c\times SU(2{)}_L\times SU(2{)}_R$. The flavor symmetry breaking scheme is considered to be $S_{3L}\times S_{3R}\to S_{2L}\times S_{2R}\to 0$. In this picture, the four-zero texture is desirable for realistic mass and mixings. This texture is realized by a specific representation for the second breaking of the $S_{3L}\times S_{3R}$ flavor symmetry. Assuming only renormalizable Yukawa interactions, type-I seesaw mechanism, and neglecting $CP$ phases for simplicity, the right-handed neutrino mass matrix $M_R$ can be reconstructed from low energy input values. Numerical analysis shows that the texture of $M_R$ basically behaves like the "waterfall texture". Since $M_R$ tends to be the "cascade texture" in the democratic texture approach, a model with type-I seesaw and up-type Yukawa unification $Y_{\nu }\simeq Y_u$ basically requires fine-tunings between parameters. Therefore, it seems to be more realistic to consider universal waterfall textures for both $Y_f$ and $M_R$, e.g., by the radiative mass generation or the Froggatt--Nielsen mechanism. Moreover, analysis of eigenvalues shows that the lightest mass eigenvalue $M_{R1}$ is too light to achieve successful thermal leptogenesis. Although the resonant leptogenesis might be possible, it also requires fine-tunings of parameters.

   hep-phPRD(2017)·6 citations
6. 06*

   A theoretical status of weak gauge boson pair production at the LHC

   Le Duc Ninh🇻🇳

   Weak gauge boson pair production is an important process at the LHC because it probes the non-Abelian structure of electroweak interactions and it is a background process for many new physics searches, and with enough statistics we can perform comparisons between measurements and theoretical calculations for different but correlated observables. In these proceedings, we present a theoretical status including state-of-the-art results from recent calculations of higher-order QCD and electroweak corrections.

   hep-ph0 citations
7. 07*

   Light Dark Matter through Assisted Annihilation

   Ujjal Kumar Dey🇮🇳 · Tarak Nath Maity🇮🇳 · Tirtha Sankar Ray🇮🇳

   In this paper we investigate light dark matter scenarios where annihilation to Standard Model particles at tree-level is kinematically forbidden. In such cases annihilation can be aided by massive Standard Model-like species, called {\it assisters}, in the initial state that enhances the available phase space opening up novel tree-level processes. We investigate the feasibility of such non-standard {\it assisted annihilation} processes to reproduce the observed relic density of dark matter. We present a simple scalar dark matter - scalar assister model where this is realised. We find that if the dark matter and assister are relatively degenerate the required relic density can be achieved for a keV-MeV scale dark matter. We briefly discuss the cosmological constraints on such dark matter scenarios.

   hep-phJCAP(2017)·53 citations
8. 08*

   Magnetic dipole moments of the negative parity $J^{PC}=2^{--}$ mesons in QCD

   T. M. Aliev (1)🇹🇷 · T. Barakat (2)🇸🇦 · M. Savcı (1) ((1) Middle East Technical University/Ankara/Turkey, (2) King Saud University/Riyadh/Saudi Arabia)🇹🇷

   Magnetic dipole moments of the negative parity light and heavy tensor mesons are calculated within the light cone QCD sum rules method. The results are compared with the positive parity counterparts of the corresponding tensor mesons. The results of the analysis show that the magnetic dipole moments of the negative parity light mesons are smaller compared to those of the positive parity mesons. Contrary to the light meson case, magnetic dipole moments of the negative parity heavy mesons are larger than the ones for the positive parity mesons.

   hep-phEPJC(2018)·2 citations
9. 09*

   Nonperturbative QED vacuum birefringence

   V.I. Denisov🇷🇺 · E.E. Dolgaya🇷🇺 · V.A. Sokolov🇷🇺

   In this paper we represent nonperturbative calculation for one-loop Quantum Electrodynamics (QED) vacuum birefringence in presence of strong magnetic field. The dispersion relations for electromagnetic wave propagating in strong magnetic field point to retention of vacuum birefringence even in case when the field strength greatly exceeds Sauter-Schwinger limit. This gives a possibility to extend some predictions of perturbative QED such as electromagnetic waves delay in pulsars neighbourhood or wave polarization state changing (tested in PVLAS) to arbitrary magnetic field values. Such expansion is especially important in astrophysics because magnetic fields of some pulsars and magnetars greatly exceed quantum magnetic field limit, so the estimates of perturbative QED effects in this case require clarification.

   hep-phJHEP(2017)·14 citations
10. 10*

    Standard Model with spontaneously broken quantum scale invariance

    D. M. Ghilencea🇷🇴 · Z. Lalak🇵🇱 · P. Olszewski🇵🇱

    We explore the possibility that scale symmetry is a quantum symmetry that is broken only spontaneously and apply this idea to the Standard Model (SM). We compute the quantum corrections to the potential of the higgs field ($\varphi$) in the classically scale invariant version of the SM ($m_{\varphi }=0$ at tree level) extended by the dilaton ($\sigma$). The tree-level potential of $\varphi$ and $\sigma$, dictated by scale invariance, may contain non-polynomial effective operators, e.g. ${\varphi }^6/{\sigma }^2$, ${\varphi }^8/{\sigma }^4$, ${\varphi }^{10}/{\sigma }^6$, etc. The one-loop scalar potential is scale invariant, since the loop calculations manifestly preserve the scale symmetry, with the DR subtraction scale $\mu$ generated spontaneously by the dilaton vev $\mu \sim ⟨\sigma ⟩$. The Callan-Symanzik equation of the potential is verified in the presence of the gauge, Yukawa and the non-polynomial operators. The couplings of the non-polynomial operators have non-zero beta functions that we can actually compute from the quantum potential. At the quantum level the higgs mass is protected by spontaneously broken scale symmetry, even though the theory is non-renormalizable. We compare the one-loop potential to its counterpart computed in the "traditional" DR scheme that breaks scale symmetry explicitly ($\mu =$constant) in the presence at the tree level of the non-polynomial operators.

    hep-phhep-thPRD(2017)·45 citations
11. 11*

    Dynamical relaxation in 2HDM models

    Zygmunt Lalak🇵🇱 · Adam Markiewicz🇵🇱

    The dynamical relaxation provides an interesting solution to the hierarchy problem in face of the missing signatures of any new physics in recent experiments. Through a dynamical process taking place in the inflationary phase of the universe it manages to achieve a small electroweak scale without introducing new states observable in current experiments. Appropriate approximation makes it possible to derive an explicit formula for the final vevs in the double-scanning scenario extended to the two Higgs doublet models (2HDM). Analysis of the relaxation in 2HDM indicates, that in a general case it is impossible to keep vevs of both scalars small, unless fine-tuning is present or additional symmetries are cast upon the Lagrangian. Within the slightly constrained variant of 2HDM, where odd powers of the fields' expectation values are not present (which can be easily enforced by requiring that the doublets have different gauge transformations or by imposing a global symmetry) it is shown that the the difference between the vevs of two scalars tends to be proportional to the cutoff. The analysis of the relaxation in 2HDM indicates, that in a~general case the relaxation would be stopped by the first doublet that gains a vev, with the other one remaining vevless with a mass of the order of the cutoff. This happens to conform with the inert doublet model.

    hep-phhep-thJ.Phys.G(2018)·12 citations
12. 12*

    Effects of Matter in Neutrino Oscillations and Determination of Neutrino Mass Hierarchy at Long-baseline Experiments

    Tomas Nosek🇨🇿

    Neutrino oscillations change when in media in comparison to vacuum oscillations due to the scattering of neutrinos on matter constituents, electrons particularly. This can be easily described by introducing new effective matter mixing angles and squared mass-splittings. Exploiting the matter effects and subsequent enhancement or suppression of oscillation probabilities can be used to determine the hierarchy of neutrino mass states. Recent long-baseline experiments NO$\nu$A and T2K investigate this possibility. Together NO$\nu$A and T2K combined can reject the wrong hierarchy for more than 20% of all possible values of yet unknown CP violating phase $\delta$ $\in$ [-180${}^{\circ }$, 180${}^{\circ }$].

    hep-phWDS'16 Proceedings of Contributed Papers …·4 citations
13. 13*

    Light weakly interacting massive particles

    Graciela B. Gelmini🇺🇸

    Light WIMPs are dark matter particle candidates with weak scale interaction with the known particles, and mass in the GeV to 10's of GeV range. Hints of light WIMPs have appeared in several dark matter searches in the last decade. The unprecedented possible coincidence into tantalizingly close regions of mass and cross section of four separate direct detection experimental hints and a potential indirect detection signal in gamma rays from the galactic center, aroused considerable interest in our field. Even if these hints did not so far result in a discovery, they have had a significant impact in our field. Here we review the evidence for and against light WIMPs as dark matter candidates and discuss future relevant experiments and observations

    hep-phRept.Prog.Phys.(2017)·31 citations
14. 14*

    Higgs Sector of the Left-Right Symmetric Theory

    Alessio Maiezza🇮🇹 · Goran Senjanović🇮🇹 · Juan Carlos Vasquez🇨🇱

    We perform an in-depth analysis of the Higgs sector in the Minimal Left-Right Symmetric Model and compute the scalar mass spectrum and associated mixings, offering simple physical and symmetry arguments in support of our findings. We identify the tree-level quartic and cubic potential couplings in terms of the physical states and compute the quantum corrections for the latter ones. The deviations from the Standard Model prediction of the cubic Higgs doublet coupling are considered. Moreover we discuss the possible implications concerning the stability of the potential under the renormalization-group-equations evolution. In particular we examine three possible energy scales of parity restoration: LHC reach, next hadronic collider and very high energy relevant for grand unification.

    hep-phhep-exPRD(2017)·84 citations
15. 15*

    Ab initio nuclear response functions for dark matter searches

    Daniel Gazda🇸🇪 · Riccardo Catena🇸🇪 · Christian Forssén🇸🇪

    We study the process of dark matter particles scattering off ${}^{3,4}$He with nuclear wave functions computed using an ab initio many-body framework. We employ realistic nuclear interactions from chiral effective field theory at next-to-next-to-leading order (NNLO) and develop an ab initio scheme to compute a general set of different nuclear response functions. In particular, we then perform an accompanying uncertainty quantification on these quantities and study error propagation to physical observables. We find a rich structure of allowed nuclear responses with significant uncertainties for certain spin-dependent interactions. The approach and results that are presented in this Paper establish a new framework for nuclear structure calculations and uncertainty quantification in the context of direct and (certain) indirect searches for dark matter.

    hep-phastro-ph.COnucl-thPRD(2017)·52 citations
16. 16*

    Flavour Structure of GUTs and Uncertainties in Proton Lifetime Estimates

    Helena Kolešová🇨🇿 · Michal Malinský🇨🇿

    We study the flavour aspects of proton lifetime estimates in simple Grand unified models paying particular attention to their inherent fragility due to the notorious lack of control of some of the key parameters governing the relevant hard-process amplitudes. Among these, the theoretical uncertainties in the flavour structure of the baryon and lepton number violating charged currents due to the potential higher-order effects afflicting the matching of the underlying Yukawa couplings to the low-energy data often play a prominent role. Focusing on the minimal variants of the most popular unified models we study the potential instabilities of the corresponding proton lifetime estimates based on the renormalizable-level Yukawa fits with respect to the Planck-scale induced flavour effects. In particular, we perform a detailed numerical analysis of all minimal $SO(10)$ Yukawa sector fits available in the literature and show that the proton lifetime estimates based on these inputs exhibit a high degree of robustness with respect to moderate-size perturbations, well within the expected "improvement window" of the upcoming proton decay searches.

    hep-phPRD(2019)·13 citations
17. 17*

    Photons and Dark Photons Through Breit-Wheeler Processes

    Ariel Arza🇨🇱 · Jorge Gamboa🇨🇱 · Natalia Tapia🇨🇱

    A variant of quantum electrodynamics coupled to a dark photon through a kinetic mixing is studied. The analogous of the light-light diagram becomes the conversion process ${\gamma }^{\prime }{\gamma }^{\prime }\to \gamma \gamma$ and an expression for the differential cross section is estimated. For high energies beams, as in LHC, this differential cross section could be measurable and its magnitude would be typically similar to the total cross section of neutrinos, {\it i.e.} $\sim 10^{-50}{\text{m}}^2$.

    hep-ph0 citations
18. 18*

    Starobinsky Inflation: From Non-SUSY To SUGRA Realizations

    C. Pallis🇨🇾 · N. Toumbas🇨🇾

    We review the realization of Starobinsky-type inflation within induced-gravity Supersymmetric (SUSY) and non-SUSY models. In both cases, inflation is in agreement with the current data and can be attained for subplanckian values of the inflaton. The corresponding effective theories retain perturbative unitarity up to the Planck scale and the inflaton mass is predicted to be 3x10^13 GeV. The supergravity embedding of these models is achieved by employing two gauge singlet chiral supefields, a superpotential that is uniquely determined by a continuous R and a discrete Zn symmetry, and several (semi)logarithmic Kaehler potentials that respect these symmetries. Checking various functional forms for the non-inflaton accompanying field in the Kaehler potentials, we identify four cases which stabilize it without invoking higher order terms.

    hep-phastro-ph.COhep-thAdv.High Energy Phys.(2017)·34 citations
19. 19*

    Excited Scalar and Pseudoscalar Mesons in the Extended Linear Sigma Model

    Denis Parganlija🇦🇹 · Francesco Giacosa🇩🇪

    We present an in-depth study of masses and decays of excited scalar and pseudoscalar $\bar{q}q$ states in the Extended Linear Sigma Model (eLSM). The model also contains ground-state scalar, pseudoscalar, vector and axial-vector mesons. The main objective is to study the consequences of the hypothesis that the $f_0(1790)$ resonance, observed a decade ago by the BES Collaboration and recently by LHCb, represents an excited scalar quarkonium. In addition we also analyse the possibility that the new $a_0(1950)$ resonance, observed recently by BABAR, may also be an excited scalar state. Both hypotheses receive justification in our approach although there appears to be some tension between the simultaneous interpretation of $f_0(1790)$/$a_0(1950)$ and pseudoscalar mesons $\eta (1295)$, $\pi (1300)$, $\eta (1440)$ and $K(1460)$ as excited $\bar{q}q$ states.

    hep-phnucl-thEPJC(2017)·39 citations
20. 20*

    Probing Doubly Charged Higgs Bosons at the LHC through Photon Initiated Processes

    K.S. Babu🇺🇸 · Sudip Jana🇺🇸

    We show that the photon-photon fusion process contributes significantly to the pair production of doubly charged Higgs bosons at the LHC at a level comparable to the Drell-Yan production. We reinterpret the ATLAS lower limit of 570 GeV (420 GeV) on the mass of ${\Delta }_L^{\pm \pm }$ (${\Delta }_R^{\pm \pm }$) arising from $SU(2{)}_L$ triplet (singlet) scalar by including the photon initiated process and derive a new lower limit of 748 GeV (570 GeV), assuming that ${\Delta }^{\pm \pm }$ decays into $e^{\pm }{e}^{\pm }$ 100% of the time. We have also shown that the 5$\sigma$ discovery reach for ${\Delta }_L^{\pm \pm }$ (${\Delta }_R^{\pm \pm }$) is 846 GeV (783 GeV) with 100 fb${}^{-1}$ luminosity at 13 TeV LHC. We derive a somewhat more stringent limit on the mass when the doubly charged scalar arises from higher dimensional representations of $SU(2{)}_L$.

    hep-phPRD(2017)·80 citations
21. 21*

    SCET for jet physics in the vacuum and the medium

    Ivan Vitev🇺🇸

    In this plenary talk I discuss soft-collinear effective theory (SCET) as a framework for precision QCD phenomenology. Emphasis is placed on jet and heavy flavor observables accessible at current and future collider facilities. One of the principal challenges that calculations of hard probes in heavy ion reactions face is the ambiguity associated with the implementation of medium-induced radiative effects. I demonstrate how extension of SCET to describe parton propagation in QCD matter has helped quantify and reduce the theoretical uncertainty in jet quenching calculations.

    hep-phNucl.Part.Phys.Proc.(2017)·1 citation
22. 22*

    The angular structure of jet quenching within a hybrid strong/weak coupling model

    Jorge Casalderrey-Solana🇬🇧 · Doga Can Gulhan🇨🇭 · Guilherme Milhano🇵🇹 · Daniel Pablos🇪🇸 · Krishna Rajagopal🇺🇸

    Building upon the hybrid strong/weak coupling model for jet quenching, we incorporate and study the effects of transverse momentum broadening and medium response of the plasma to jets on a variety of observables. For inclusive jet observables, we find little sensitivity to the strength of broadening. To constrain those dynamics, we propose new observables constructed from ratios of differential jet shapes, in which particles are binned in momentum, which are sensitive to the in-medium broadening parameter. We also investigate the effect of the back-reaction of the medium on the angular structure of jets as reconstructed with different cone radii R. Finally we provide results for the so called "missing-pt", finding a qualitative agreement between our model calculations and data in many respects, although a quantitative agreement is beyond our simplified treatment of the hadrons originating from the hydrodynamic wake.

    hep-phNucl.Part.Phys.Proc.(2017)·1 citation
23. 23*

    Radiative 3He-alpha reaction in Halo Effective Field Theory

    Renato Higa🇧🇷 · Gautam Rupak🇺🇸 · Akshay Vaghani🇺🇸

    In this work we study the radiative capture of ${}^3\mathrm{He}$ on ${}^4\mathrm{He}$ within the halo effective field theory (EFT) framework. At leading order the capture amplitude comprises the initial state $s$-wave strong and Coulomb interactions summed to all orders. At the same order in the expansion, leading two-body currents contribute as well. We find delicate cancelations between the various contributions, and the two-body current contributions can be replaced by appropriately enhancing the asymptotic normalizations of the ${}^7$Be ground and first excited state wave functions. The next-to-leading order corrections come from the $s$-wave shape parameter and the pure Coulomb $d$-wave initial state interactions. We fit the EFT parameters to available scattering data and most recent capture data. Our zero-energy astrophysical $S$-factor estimate, $S_{34}\sim 0.55$ keV b, is consistent within error bars with the average in the literature.

    ↳ nucl-thastro-ph.SRhep-phnucl-exEPJA(2018)·46 citations
24. 24*

    Impact of Lattice QCD on CKM Phenomenology

    Monika Blanke🇩🇪

    Precise lattice QCD results for hadronic matrix elements, decay constants and form factors play a crucial role in the determination of CKM matrix elements and in the identification of possible new physics contributions to flavour violating observables. This article reviews the implications of recent lattice QCD results on the phenomenology of flavour and CP violating meson decays, and highlights some future directions for lattice QCD calculations which would have a major impact on flavour phenomenology.

    ↳ hep-lathep-phPoS(2016)·2 citations
25. 25*

    Spectral and Transport Properties of Quark-Gluon Plasma in a Nonperturbative Approach

    Shuai Y.F. Liu🇺🇸 · Ralf Rapp🇺🇸

    Nonperturbative methods play an important role in quantum many-body systems, especially in situations with an interplay of continuum and bound states and/or large coupling strengths between the constituents. Employing the Luttinger-Ward functional (LWF) we have computed the equation of state (EoS) of the quark-gluon plasma (QGP) using fully dressed selfconsistent 1- and 2-body propagators. We first give an alternative derivation of our previously reported results for resumming the ladder diagram series of the LWF using a "matrix log" technique which accounts for dynamically formed bound and resonant states. Two types of solutions were found in selfconsistent fits to lattice-QCD data for the EoS, heavy-quark free energy and quarkonium correlators: a strongly coupled scenario (SCS) with broad parton spectral functions and strong meson resonances near the transition temperature vs. a weakly coupled scenario (WCS) with well-defined parton quasiparticles and weak meson resonances. Here, we discuss how these solutions can be distinguished by analyzing the pertinent transport properties. We focus on the specific shear viscosity, $(4\pi )\eta /s$, and the heavy-quark diffusion coefficient, $(2\pi T){\mathcal{D}}_s$, including its mass dependence. At low temperatures, in the SCS, they turn out to be a factor of 2 within their conjectured quantum lower bound, while they are a factor of 2-5 larger in the WCS. At higher temperatures, the transport parameters of the two scenarios approach each other. We propose the ratio $(4\pi \eta /s)/(2\pi T{\mathcal{D}}_s)$ as a measure to distinguish the perturbative and strong-coupling limits of 5/2 and 1, respectively.

    ↳ nucl-thcond-mat.quant-gascond-mat.stat-mechhep-ph+1EPJA(2020)·70 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.