Publications

Order by: publication date number of citations

• Completeness of the Bethe states for the rational, spin-1/2 Richardson-Gaudin system

  Jon Links

  SciPost Phys. 3, 007 (2017) · published 28 July 2017 | Toggle abstract · pdf

  Establishing the completeness of a Bethe Ansatz solution for an exactly solved model is a perennial challenge, which is typically approached on a case by case basis. For the rational, spin-1/2 Richardson--Gaudin system it will be argued that, for generic values of the system's coupling parameters, the Bethe states are complete. This method does not depend on knowledge of the distribution of Bethe roots, such as a string hypothesis, and is generalisable to a wider class of systems.

  15 citations

• Phases of cold holographic QCD: Baryons, pions and rho mesons

  Nicolas Kovensky, Aaron Poole, Andreas Schmitt

  SciPost Phys. 15, 162 (2023) · published 13 October 2023 | Toggle abstract · pdf

  We improve the holographic description of isospin-asymmetric baryonic matter within the Witten-Sakai-Sugimoto model by accounting for a realistic pion mass, computing the pion condensate dynamically, and including rho meson condensation by allowing the gauge field in the bulk to be anisotropic. This description takes into account the coexistence of baryonic matter with pion and rho meson condensates. Our main result is the zero-temperature phase diagram in the plane of baryon and isospin chemical potentials. We find that the effective pion mass in the baryonic medium increases with baryon density and that, as a consequence, there is no pion condensation in neutron-star matter. Our improved description also predicts that baryons are disfavored at low baryon chemical potentials even for arbitrarily large isospin chemical potential. Instead, rho meson condensation sets in on top of the pion condensate at an isospin chemical potential of about $9.4 m_\pi$. We further observe a highly non-monotonic phase boundary regarding the disappearance of pion condensation.

  13 citations

• Four-quark scatterings in QCD I

  Wei-jie Fu, Chuang Huang, Jan M. Pawlowski, Yang-yang Tan

  SciPost Phys. 14, 069 (2023) · published 13 April 2023 | Toggle abstract · pdf

  We investigate dynamical chiral symmetry breaking and the emergence of mesonic bound states from the infrared dynamics of four-quark scatterings. Both phenomena originate from the resonant scalar-pseudoscalar channel of the four-quark scatterings, and we compute the functional renormalisation group (fRG) flows of the Fierz-complete four-quark interaction of up and down quarks with its $t$ channel momentum dependence. This is done in the isospin symmetric case, also including the flow of the quark two-point function. This system can be understood as the fRG analogues of the complete Bethe-Salpeter equations and quark gap equation. The pole mass of the pion is determined from both direct calculations of the four-quark flows in the Minkowski regime of momenta and the analytic continuation based on results in the Euclidean regime, which are consistent with each other.

  11 citations

• Speed of sound in dense strong-interaction matter

  Jens Braun, Andreas Geißel, Benedikt Schallmo

  SciPost Phys. Core 7, 015 (2024) · published 5 April 2024 | Toggle abstract · pdf

  We study the speed of sound in strong-interaction matter at zero temperature and in density regimes which are expected to be governed by the presence of a color-superconducting gap. At (very) high densities, our analysis indicates that the speed of sound approaches its asymptotic value associated with the non-interacting quark gas from below, in agreement with first-principles studies which do not take the presence of a color-superconducting gap into account. Towards lower densities, however, the presence of a gap induces an increase of the speed of sound above its asymptotic value. Importantly, even if gap-induced corrections to the pressure may appear small, we find that derivatives of the gap with respect to the chemical potential can still be sizeable and lead to a qualitative change of the density dependence of the speed of sound. Taking into account constraints on the density dependence of the speed of sound at low densities, our general considerations suggest the existence of a maximum in the speed of sound. Interestingly, we also observe that specific properties of the gap can be related to characteristic properties of the speed of sound which are indirectly constrained by observations.

  9 citations

• A no-go theorem for non-standard explanations of the $\tau\to K_S\pi\nu_\tau$ CP asymmetry

  Vincenzo Cirigliano, Andreas Crivellin, Martin Hoferichter

  SciPost Phys. Proc. 1, 007 (2019) · published 18 February 2019 | Toggle abstract · pdf

  A new tensor interaction is the only possibility to explain the $2.8\sigma$ tension observed by the BaBar collaboration in the CP asymmetry in $\tau\to K_S\pi\nu_\tau$ with physics beyond the Standard Model (BSM) realized above the electroweak scale. However, the strong phase generated by the interference between vector and tensor phases is suppressed by at least two orders of magnitude due to Watson's final-state-interaction theorem, and the strength of the CP-violating tensor interaction is strongly constrained by bounds from the neutron electric dipole moment and $D$-$\bar{D}$ mixing. As a result, a confirmation of the tension at Belle II would point to light BSM physics.

  9 citations

• Jets in Evolving Matter within the Opacity Expansion Approach

  Andrey V. Sadofyev, Matthew D. Sievert, Ivan Vitev

  SciPost Phys. Proc. 8, 046 (2022) · published 12 July 2022 | Toggle abstract · pdf

  In a recent study [1] we have extended the opacity expansion approach to describe jet-medium interactions including medium motion effects in the context of heavy-ion collisions. We have computed color field of the in-medium sources, including the effects of the transverse field components and the energy transfer between the medium and jet. The corresponding contributions are sub-eikonal in nature, and were previously ignored in the literature. Here we discuss how our approach can be applied to describe the medium motion effects in the context of Deep Inelastic Scattering.

  7 citations

• Many phases of generalized 3D instanton crystals

  Matti Jarvinen, Vadim Kaplunovsky, Jacob Sonnenschein

  SciPost Phys. 11, 018 (2021) · published 23 July 2021 | Toggle abstract · pdf

  Nuclear matter at large number of colors is necessarily in a solid phase. In particular holographic nuclear matter takes the form of a crystal of instantons of the flavor group. In this article we initiate the analysis of the three-dimensional crystal structures and the orientation patterns for the two-body potential that follows from holographic duality. The outcome of the analysis includes several unexpected results. We perform simulations of ensembles of O(10000) instantons whereby we identify the lattice structure and orientations for the different values of the weight factors of the non-Abelian orientation terms in the two-body potential. The resulting phase diagram is surprisingly complex, including a variety of ferromagnetic and antiferromagnetic crystals with various global orientation patterns, and various "non-Abelian" crystals where orientations have no preferred direction. The latter include variants of face-centered-cubic, hexagonal, and simple cubic crystals which may have remarkably large or small aspect ratios. The simulation results are augmented by analytic analysis of the long-distance divergences, and numerical computation of the (divergence free) energy differences between the non-Abelian crystals, which allows us to precisely determine the structure of the phase diagram.

  7 citations

• Predictions for neutron stars from holographic nuclear matter

  Nicolas Kovensky, Aaron Poole, Andreas Schmitt

  SciPost Phys. Proc. 6, 019 (2022) · published 31 May 2022 | Toggle abstract · pdf

  We discuss masses, radii, and tidal deformabilities of neutron stars constructed from the holographic Witten-Sakai-Sugimoto model. Using the same model for crust and core of the star, we combine our theoretical results with the latest astrophysical data, thus deriving more stringent constraints than given by the data alone. For instance, our calculation predicts - independent of the model parameters - an upper limit for the maximal mass of the star of about 2.46 solar masses and a lower limit of the (dimensionless) tidal deformability of a 1.4-solar-mass star of about 277.

  6 citations

• QCD factorization for hadronic quarkonium production at high $p_T$

  Kyle Lee, Jian-Wei Qiu, George Sterman, Kazuhiro Watanabe

  SciPost Phys. Proc. 8, 143 (2022) · published 14 July 2022 | Toggle abstract · pdf

  Heavy quarkonium production at high transverse momentum ($p_T$) in hadronic collisions is explored in the QCD factorization approach. We find that the leading power in the $1/p_T$ expansion is responsible for high $p_T$ regime, while the next-to-leading power contribution is necessary for the low $p_T$ region. We present the first numerical analysis of the scale evolution of coupled twist-2 and twist-4 fragmentation functions (FFs) for heavy quarkonium production and demonstrate that the QCD factorization approach is capable of describing the $p_T$ spectrum of hadronic $J/\psi$ production at the LHC.

  6 citations

• Four-quark scatterings in QCD II

  Wei-jie Fu, Chuang Huang, Jan M. Pawlowski, Yang-yang Tan

  SciPost Phys. 17, 148 (2024) · published 29 November 2024 | Toggle abstract · pdf

  In [SciPost Phys. 14, 069 (2023)], we initiated a program for the quantitative investigation of dynamical chiral symmetry breaking and resonant bound states in QCD with the functional renormalisation group, concentrating on the full infrared dynamics of four-quark scatterings. In the present work we extend this study and take into account a three-momentum channel approximation ($s,t,u$-channel) for the Fierz-complete four-quark vertices. We find that the four-quark vertex in this approximation is quantitatively reliable. In particular, we have computed the pion pole mass, pion decay constant, Bethe-Salpeter amplitudes, the quark mass function and wave function. Our results confirm previous findings that low energy effective theories only reproduce QCD quantitatively, if initiated with a relatively low ultraviolet cutoff scale of the order of 500 MeV. The quantitative description set up here paves the way for reliable quantitative access to the resonance structure in QCD within the fRG approach to QCD.

  6 citations