Flavor quark at high temperature from a holographic model

TL;DR

This work investigates a holographic realization of QCD-like physics with light flavor quarks by embedding a D7 brane in a finite-temperature, dilaton-deformed AdS background. By analyzing the D7 embedding, Wilson-Polyakov loops, and two quark-antiquark string configurations, the authors identify a temperature-driven phase transition and compute the quark mass, potential, and screening behavior, comparing two backgrounds (gauge-field condensate and D4-D6). They find no spontaneous chiral symmetry breaking in the deconfined phase, a finite-range quark-antiquark potential below a critical temperature $T_{\text{fund}}$, and bound-state remnants (mesons and metastable baryons) that disappear above this scale, broadly consistent with lattice QCD expectations. The results illuminate how deconfinement and bound-state survival emerge in holographic models and suggest a universal deconfinement threshold independent of the specific background. The approach, working in the large-$N_c$ limit with a probe D7 brane, captures qualitative QCD features and provides insight into temperature-dependent hadron spectra in strongly coupled gauge theories.

Abstract

Gauge theory with light flavor quark is studied by embedding a D7 brane in a deconfinement phase background newly constructed. We find a phase transition by observing a jump of the vacuum expectation value of quark bilinear and also of the derivative of D7 energy at a critical temperature. For the model considered here, we also study quark-antiquark potential to see some possible quark-bound states and other physical quantities in the deconfinement phase.

Figures (10)

• Figure 1: Embedding solutions for $q=0$. The solutions are drawn for several temperatures, where $m_q=0.91$ and $\pi R^2=1$.
• Figure 2: Embedding solutions for $q/T^4=0.1$ and $m_q=0.91$. The way of the embedding changes at $T = 0.94\sim 0.95$ in unit of $\pi R^2=1$.
• Figure 3: The temperature dependence of the chiral condensate: for $m_q = 0.91$ and $\pi R^2=1$.
• Figure 4: The temperature dependence of the regularized energy: for $m_q = 0.91$ and $\pi R^2=1$. The vertical line denotes $T=T_{\textrm{\scriptsize fund}}$. The right figure shows the neighborhood of the transition point. The dashed lines stand for the slops at the transition point.
• Figure 5: $\tilde{m}_q$ are shown for $R=1/\sqrt{\pi} (\hbox{GeV}^{-1})$, $r_{\textrm{\scriptsize max}}=10 (\hbox{GeV}^{-1})$ and $\alpha'=10^3 (\hbox{GeV}^{-2})$. The three solid curves are corresponding to the case of $q=0,~10^3$ and $2\times 10^3 (\hbox{GeV}^{-4})$, respectively. The dashed curve represents the result for the D4-D6 model (\ref{['dynamicalmass46']}) with $R =10 (3/{4\pi})^{2/3}$, $r_{\textrm{\scriptsize max}}=200$ and $\alpha'=10^3$. The points represent the lattice data lattice.