QCD critical end point from a realistic PNJL model

With parameters fixed by critical temperature and equation of state at zero baryon chemical potential, a realistic Polyakov--Nambu--Jona-Lasinio (rPNJL) model predicts a critical end point of chiral phase transition at $(\mu_B^E= 720 {\rm MeV}, T^E=93 {\rm MeV})$. The extracted freeze-out line from heavy ion collisions is close to the chiral phase transition boundary in the rPNJL model, and the kurtosis $\kappa \sigma^2$ of baryon number fluctuations from the rPNJL model along the experimental freeze-out line agrees well with the BES-I measurement. Our analysis shows that the dip structure of measured $\kappa\sigma^2$ is determined by the relationship between the freeze-out line and chiral phase transition line at low baryon density region, and the peak structure can be regarded as a clean signature for the existence of CEP.Comment: 8 papges, proceedings of QCD@Work 201

Corrections to holographic entanglement plateau

We investigate the robustness of the Araki-Lieb inequality in a two-dimensional (2D) conformal field theory (CFT) on torus. The inequality requires that $\Delta S=S(L)-|S(L-\ell)-S(\ell)|$ is nonnegative, where $S(L)$ is the thermal entropy and $S(L-\ell)$, $S(\ell)$ are the entanglement entropies. Holographically there is an entanglement plateau in the BTZ black hole background, which means that there exists a critical length such that when $\ell \leq \ell_c$ the inequality saturates $\Delta S=0$. In thermal AdS background, the holographic entanglement entropy leads to $\Delta S=0$ for arbitrary $\ell$. We compute the next-to-leading order contributions to $\Delta S$ in the large central charge CFT at both high and low temperatures. In both cases we show that $\Delta S$ is strictly positive except for $\ell = 0$ or $\ell = L$. This turns out to be true for any 2D CFT. In calculating the single interval entanglement entropy in a thermal state, we develop new techniques to simplify the computation. At a high temperature, we ignore the finite size correction such that the problem is related to the entanglement entropy of double intervals on a complex plane. As a result, we show that the leading contribution from a primary module takes a universal form. At a low temperature, we show that the leading thermal correction to the entanglement entropy from a primary module does not take a universal form, depending on the details of the theory.Comment: 32 pages, 8 figures; V2, typos corrected, published versio

Using neutron scattering to study the structure and flexibility of hexadecyltrimethylammonium dichlorobenzoate and related micelles

Certain ionic surfactants can self-assemble in aqueous solutions into giant flexible wormlike micelles that behave similarly to semi-flexible polymers. Small angle neutron scattering (SANS) has been used to study the sizes and flexibilities of these micelles. By allowing the probing of shorter length scales than light scattering, SANS is clearly preferable for determining micellar persistence lengths directly. SANS curves were fit to a series of micellar models to get information on persistence lengths, contour lengths and cross-sectional radii. The impact of different tail lengths, head groups, counterions, and varying ionic strengths were studied. Counterions have major effects on micellar size and flexibility. For nonpenetrating counterions, such as chloride and bromide, the micellar size and flexibility increase as the concentrations of the counterion increase (by adding the common-ion salt), with bromide having the larger effect compared to chloride. For penetrating counterions, such as salicylate, 26dichlorobenzoate, and tosylate, the micellar size and flexibility highly depend on the structure of the counterions. Mixed counterions (penetrating and non penetrating) have also been studied, and the micellar size found to increase dramatically in mixed counterions systems