Bump of sound velocity in dense 2-color QCD

Etsuko Itou; Kei Iida

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Bump of sound velocity in dense 2-color QCD

Etsuko Itou, Kei Iida

High Energy Physics - Lattice · Submitted 25 Oct 2022

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim We obtain the equation of state (EoS) and the sound velocity for 2-color QCD at low temperature and high density and find that in the superfluid phase, $c_s^2/c^2 >1/3$, where $1/3$ is the value at the relativistic limit.

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What the abstract itself states, as probabilities: claims first 0.04 · states limitation 0.18 · human participants 0.01 · controlled comparison 0.18 · randomized assignment 0.01 · states quantitative result 0.97 · compares with prior results 0.94 · mentions code or data availability 0.02.

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We obtain the equation of state (EoS) and the sound velocity for 2-color QCD at low temperature and high density and find that in the superfluid phase, $c_s^2/c^2 >1/3$, where $1/3$ is the value at the relativistic limit. Several independent Monte Carlo studies on 2-color QCD have been conducted intensively in recent years. These works have shown a clear evidence of phase transition between hadronic and superfluid phases. In our paper[1], we have investigated the EoS and sound velocity in both phases. Our result is consistent with chiral perturbation theory in a low $\mu$ regime of the superfluid phase including the Bose-Einstein condensed phase, and shows a peak of sound velocity in the high-density BCS phase. We also give detailed simulation results and a comment on the holography bound in this proceedings.

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#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We obtain the equation of state (EoS) and the sound velocity for 2-color QCD at low temperature and high density and find that in the superfluid phase, $c_s^2/c^2 >1/3$, where $1/3$ is the value at the relativistic limit.	result 0.98	0.97	0.87	asserted 1.00
s1	Several independent Monte Carlo studies on 2-color QCD have been conducted intensively in recent years.	background 1.00	0.04	0.02	asserted 1.00
s2	These works have shown a clear evidence of phase transition between hadronic and superfluid phases.	background 1.00	0.05	0.03	asserted 1.00
s3	In our paper[1], we have investigated the EoS and sound velocity in both phases.	contribution 0.95	0.94	0.05	asserted 0.98
s4	Our result is consistent with chiral perturbation theory in a low $\mu$ regime of the superfluid phase including the Bose-Einstein condensed phase, and shows a peak of sound velocity in the high-density BCS phase.	result 0.82	0.93	0.29	asserted 0.70
s5	We also give detailed simulation results and a comment on the holography bound in this proceedings.	contribution 0.97	0.86	0.03	asserted 0.97

What kind of paper the classifier reports this is: simulation study 1.00 · evidence from simulation or computation 1.00.

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Original abstract

We obtain the equation of state (EoS) and the sound velocity for 2-color QCD at low temperature and high density and find that in the superfluid phase, $c_s^2/c^2 >1/3$, where $1/3$ is the value at the relativistic limit. Several independent Monte Carlo studies on 2-color QCD have been conducted intensively in recent years. These works have shown a clear evidence of phase transition between hadronic and superfluid phases. In our paper[1], we have investigated the EoS and sound velocity in both phases. Our result is consistent with chiral perturbation theory in a low $\mu$ regime of the superfluid phase including the Bose-Einstein condensed phase, and shows a peak of sound velocity in the high-density BCS phase. We also give detailed simulation results and a comment on the holography bound in this proceedings.

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6 arXiv papers cite this in 11 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers whose main result relates to this one's

Found among the papers closest to this one by title and main claim. Pith's classifier compared each pair's main results and a second model family confirmed the relation; checked against two further families, shown conflicts agreed 118 times in 120 and shown same results 218 times in 239. The quoted sentence is the other paper's main claim.

States the same result 2 papers

We find that the velocity of sound exceeds the relativistic limit ($c_s^2/c^2=1/3$) after BEC-BCS crossover in the superfluid phase.

Velocity of Sound beyond the High-Density Relativistic Limit from Lattice Simulation of Dense Two-Color QCD · 0.98
However, our recent work~\cite{Iida:2022hyy} shows the breaking of this bound in dense QC$_2$D.

Speed of sound exceeding the conformal bound in dense 2-color QCD · 0.90

Papers citing it · 4 sentences without a confident label

Uses its method or tool 2 papers

At nonzero chemical potential, one can follow a similar strategy to calculate the modifications of pressure and interaction measure using $μ=0$ subtraction (see, e.g., Ref. [ref] and Refs. [ref] ).

Equation of state and speed of sound of isospin-asymmetric QCD on the lattice · The EoS from an interpolation of the isospin density · 0.91
We use the same lattice setup as that used in our previous works [ref] .

Chemical potential (in)dependence of hadron scatterings in the hadronic phase of QCD-like theories and its applications · Lattice Setups · 0.98

Compares with it 3 papers

The non-monotonic profile of $C^2_S$ [ref] becomes apparent and visible as $κ→1$ , similar to inferred in numerous works for cold NS matter [ref] and contrary to the results in Ref. [ref] .

Observables and conformal properties of dark matter admixed isentropic neutron stars · Speed of Sound · 0.83
We note that our finding of $c_s^2>1/3$, as well as the development of a peak is in good agreement with recent results obtained in two-color QCD [ref] (see also [ref] ).

Equation of state and speed of sound of isospin-asymmetric QCD on the lattice · Speed of sound at vanishing temperature · 0.98
Our findings are in good agreement with recent results obtained in two-color QCD [ref] .

Equation of state and Taylor expansions at nonzero isospin chemical potential · The speed of sound · 0.99

Cites it as background 1 paper

In recent years, lattice Monte Carlo studies on dense QC$_2$D have been conducted independently and intensively by several groups [ref] .

Lattice study on finite density QC$_2$D towards zero temperature · Introduction · 0.95

What it cites · 15 sentences without a confident label

Uses the method or tool of 2 papers

Now, we utilize a fixed scale method to obtain the EoS at finite density [ref] .

Deconfinement in dense 2-color QCD · Equation of state and velocity of sound at finite $μ$ · 1.00
To obtain the extrapolated value at $j=0$, we perform the reweighting of $j$ and take the linear extrapolation (see Fig.8 in Ref. [ref] ).

Two-colour QCD phases and the topology at low temperature and high density · Simulation results · 0.97

Uses data or values from 1 paper

phase structure in Fig. [ref] and summarize the definition of each phase in Table [ref], which is an extract from Ref. [ref] .

Two-colour QCD phases and the topology at low temperature and high density · Phase structure at $T=79$ MeV · 0.84

Compares with 4 papers

First of all, our results are consistent with the prediction of ChPT [ref] , which is given by $c_s^2/c^2=(1-μ_c^4/μ^4)/(1+3μ_c^4/μ^4)$, in the BEC phase.

Deconfinement in dense 2-color QCD · Simulation results · 0.93
On the other hand, a result based on the resummed perturbation theory suggests that $c_s^2/c^2$ approaches the limit from above [ref] .

Equation of state of cold and dense QCD matter in resummed perturbation theory · Summary and discussion · 0.92
For example, in the finite temperature case, the sound velocity monotonically increases in $T>T_c$ and approaches the relativistic limit as the temperature increases [ref] .

Full result for the QCD equation of state with 2+1 flavors · Simulation results · 0.93

Cites as support 2 papers

It supports the predictions from several effective models based on the presence of the quark Fermi sea [ref] .

Stiffening of matter in quark-hadron continuity · Summary and discussion · 0.96
It supports the predictions from several effective models based on the presence of the quark Fermi sea [ref] .

Peaks of sound velocity in two color dense QCD: quark saturation effects and semishort range correlations · Summary and discussion · 0.96

Cites as background 2 papers

Based on this motivation, several Monte Carlo studies on $2$-color QCD have been conducted independently and intensively in recent years (see references in Ref. [ref] ).

Velocity of Sound beyond the High-Density Relativistic Limit from Lattice Simulation of Dense Two-Color QCD · Introduction · 0.93
Several early works based on a phenomenological quark-hadron crossover picture of neutron star matter [ref] suggested that the zero-temperature sound velocity squared, $c_s^2=∂p/∂e$, peaks in $n_B = 1$–$10n_o$ to be consistent with various observational constraints.

From hadrons to quarks in neutron stars: a review · Introduction · 0.91

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