[Paper Review] Fractionalized Quasiparticles and the Hadron-Quark Duality in Dense Baryonic Matter

Mannque Rho|arXiv (Cornell University)|May 13, 2020

Cold Atom Physics and Bose-Einstein Condensates4 citations

TL;DR

This paper proposes a novel duality framework in dense baryonic matter where fractionalized quasiparticles—specifically half-skyrmions and FQH-like pita-like droplets—replace conventional baryons at high densities in compact stars. By unifying hadronic and quark-like degrees of freedom via hidden local symmetry (ρ, ω) and scale symmetry (dilaton χ), it suggests that the transition to deconfined quark matter is not a phase transition but a smooth duality, with fractional baryon charges (1/2, 1/3) emerging as effective quasiparticles in a Fermi liquid-like state before deconfinement.

ABSTRACT

I discuss a novel scenario on how baryonic matter could turn into a Fermi liquid of fractionalized baryons driven by high density inside compact stars. It involves the "hidden" local vector bosons $\ ho$ and $\\omega$ together with the "hidden" scale symmetry dilaton $\\chi$, both taken to be "dual" to the quarks and gluons of QCD in the sense of quark $\\leftrightarrow$ hadron duality and offers a possibility, exploiting the "Cheshire Cat Principle", to unify the "dichotomy" of baryons described in terms of skyrmions and fractional quantum Hall (FQH) droplets {\\it and} to explore how the baryonic matter could behave as density goes way beyond the normal nuclear matter density to the density regime where "deconfined" quarks are presumed to figure. The question is raised as to whether the fractionalized characteristics of the "stuff" -- whatever they are -- can be "probed" in the dense star core of compact stars.

Motivation & Objective

• To resolve the long-standing dichotomy between baryonic matter described by skyrmions and quark matter described by quasiquarks in dense compact stars.
• To explore whether fractionalized quasiparticles with baryon charge 1/3 or 1/2 can emerge as effective degrees of freedom in high-density baryonic matter before full deconfinement.
• To unify the description of dense matter using hidden local symmetry (ρ, ω) and scale symmetry (dilaton χ), treating them as dual to QCD quarks and gluons.
• To investigate whether the Fermi liquid behavior of quasiparticles persists at high densities, even as the system approaches the dilaton limit fixed point.
• To propose that the observed properties of massive neutron stars (e.g., >2M⊙) may be explained by a precursor state of fractionalized quasiparticles rather than a sharp phase transition to quark matter.

Proposed method

• Formulates a field-theoretic model based on hidden local symmetry (HLS) and scale symmetry (dilaton χ), treating ρ and ω as dual to QCD vector currents.
• Introduces the concept of 'half-skyrmions' as topological solitons in dense matter, which can be viewed as fractionalized baryonic quasiparticles with charge 1/2.
• Models the dense medium as a stack of FQH-type pita-like droplets (analogous to quantum Hall states), with tunneling between layers mediated by Chern-Simons-like topological fields.
• Applies the Cheshire Cat Principle to unify the description of baryons as skyrmions and as fractional quantum Hall droplets via topological duality.
• Uses effective field theory (GnEFT) to describe the half-skyrmion phase, linking it to the observed properties of massive neutron stars.
• Extends the Landau Fermi liquid framework to high densities by allowing topological changes in the Fermi surface, with parameters modified by the emergence of hidden symmetries.

Experimental results

Research questions

• RQ1 Can fractionalized quasiparticles with baryon charge 1/3 or 1/2 emerge as effective degrees of freedom in dense baryonic matter, even before deconfinement?
• RQ2 How does the hadron-quark duality manifest in the absence of a sharp phase transition, and what role do hidden local and scale symmetries play?
• RQ3 To what extent can the half-skyrmion structure in dense matter be mapped to a fractional quantum Hall state, and what are the implications for the equation of state?
• RQ4 Can the observed properties of massive neutron stars (e.g., mass >2M⊙) be explained by a precursor state of fractionalized quasiparticles rather than a phase transition to quark matter?
• RQ5 What is the role of the η′ meson and dilaton field in stabilizing the half-skyrmion phase and delaying the onset of true deconfinement?

Key findings

• The half-skyrmion phase in dense baryonic matter can be described as a Fermi liquid of fractionalized quasiparticles with baryon charge 1/2, stabilized by hidden local symmetry and scale invariance.
• The transition from baryonic matter to a deconfined quark phase is not a phase transition but a duality, with the same effective degrees of freedom (quasiparticles) describing both regimes.
• The model predicts that the effective baryon charge of quasiparticles evolves from 1 (at normal nuclear density n₀ ≈ 0.16 fm⁻³) to 1/2 and eventually to 1/3 as density increases, reflecting topological changes in the Fermi surface.
• The emergence of a Chern-Simons structure in the stack of FQH-type pita layers provides a mechanism for fractionalization, analogous to spinons in quantum magnets.
• The model explains the observed mass of massive neutron stars (>2M⊙) without requiring a sharp deconfinement transition, suggesting that the half-skyrmion phase is a stable precursor to the quark phase.
• The dilaton limit fixed point (where chiral symmetry is restored) is approached only at densities n ≳ 25n₀, well beyond the core densities of stable compact stars, implying that Fermi liquid behavior remains valid in observable regimes.