Zeros of the partition function for 12 flavor QCD
12味QCD配分函数的零点
Anas Saleh, Michael Hite, Diego Floor, Yannick Meurice
AI总结 通过重构态密度和计算配分函数零点,研究12味交错费米子SU(3)格点规范理论中的相变,发现m_q=0.02时存在一级相变,并估计临界质量m_q^c~0.05。
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我们考虑一个四维$SU(3)$格点规范理论,包含12个具有相同质量和未改进作用的交错费米子。利用不同逆裸耦合$\beta$下的plaquette分布集合,我们通过Ferrenberg-Swendsen方法重构态密度,并计算在裸夸克质量$m_q$ = 0.02, 0.06, 0.08和0.1时,对于线性尺寸$L$= 4, 6, 8, 10和12的超立方体,配分函数在复$\beta$平面上的零点。我们的假设是在$(m_q,\beta)$平面上存在一条一级相变线,终止于二级相变点。我们预期该相变属于4D Ising平均场普适类。我们使用两参数($y = bL^{-d}$)和三参数($y = a + bL^{-d}$)拟合来拟合具有最低虚部的零点的$L$依赖性。对于$m_q$ = 0.02,结果为一级相变提供了强有力的支持($d=3.98(6)$,且$a$在统计上与0兼容)。结果还表明,对于$m_q=0.06$,统计显著性较低,其他三个质量高于临界值$m_q^c$。此外,我们提出最低零点$a$的无穷体积间隙可以表示为$a\simeq A(m_q-m_q^c)^{B}$,其中$m_q^c\sim 0.05$,$B\sim 1$。鉴于只有三个数据点且误差较大,很难排除平均场值$B=3/2$。将该结果与Jin和Mawhinney的光谱结果结合,表明与实轴的间隙(Lee-Yang边)大致按$m_\sigma ^2$标度,其中$m_\sigma$是$0^{++}$标量粒子的质量,也是最低激发态。
We consider a four dimensional $SU(3)$ lattice gauge theory with 12 staggered fermions having identical masses and an unimproved action. Using sets of plaquette distributions for various inverse bare couplings $β$, we reconstruct the density of states with the Ferrenberg -Swendsen method and calculate the zeros of the partition in the complex $β$ plane with bare quark masses $m_q$ = 0.02, 0.06, 0.08 and 0.1 for hypercubes of linear size $L$= 4, 6, 8, 10, and 12. Our hypothesis is that there is a line of first order transitions in the $(m_q,β)$ plane ending at a second order phase transition. We expect this transition to be in the 4D Ising, mean field, universality class. We fit the $L$ dependence of the zeros with the lowest imaginary part using two ($y = bL^{-d}$) and three ($y = a + bL^{-d}$) parameter fits. For $m_q$ = 0.02 the results provide strong support for a first order phase transition ($d=3.98(6)$, and $a$ statistically compatible with 0). The results also indicate, with less statistical significance for $m_q=0.06$, that the three other masses are above the critical value $m_q^c$. In addition, we suggest that the infinite volume gap for the lowest zero $a$, can be represented as $a\simeq A(m_q-m_q^c)^{B}$ with $m_q^c\sim 0.05$ and $B\sim 1$. Given that there are only three data points with significant error bars, it is difficult to rule out the mean field value $B=3/2$. Combining this result with spectroscopic results by Jin and Mawhinney, indicates that the gap with real axis (Lee-Yang edge) scales roughly like $m_σ^2$, where $m_σ$ is the mass of the $0^{++}$ scalar which is also the lowest excitation.