arXiv subjects

K. Zambello

Publications and source records attributed to K. Zambello.

5 recordsLinked to original sources

arXiv2024

Searching for the QCD critical point using Lee-Yang edge singularities

Using $N_f=2+1$ QCD calculations at physical quark mass and purely imaginary baryon chemical potential, we locate Lee-Yang edge singularities in the complex chemical potential plane. These singularities have been obtained by the multi-point Padé approach applied to the net baryon number density. We recently showed that singularities extracted with this approach are consistent with universal scaling near the Roberge-Weiss transition. Here we study the universal scaling of these singularities in the vicinity of the QCD critical endpoint. Making use of an appropriate scaling ansatz, we extrapolate these singularities on $N_τ=6$ and $N_τ=8$ lattices towards the real axis to estimate the position of a possible QCD critical point. We find an approach toward the real axis with decreasing temperature. We compare this estimate with a HotQCD estimate obtained from poles of a [4,4]-Padé resummation of the eighth-order Taylor expansion of the QCD pressure.

hep-lat↗

arXiv2024

Detecting Lee-Yang/Fisher singularities by multi-point Padè

The Bielefeld Parma Collaboration has in recent years put forward a method to probe finite density QCD by the detection of Lee-Yang singularities. The location of the latter is obtained by multi-point Padè approximants, which are in turn calculated matching Taylor series results obtained from Monte Carlo computations at (a variety of values of) imaginary baryonic chemical potential. The method has been successfully applied to probe the Roberge Weiss phase transition and preliminary, interesting results are showing up in the vicinity of a possible QCD critical endpoint candidate. In this talk we will be concerned with a couple of significant aspects in view of a more powerful application of the method. First, we will discuss the possibility of detecting finite size scaling of Lee-Yang/Fisher singularities in finite density (lattice) QCD. Second, we will briefly mention our attempts at detecting both singularities in the complex chemical potential plane and singularities in the complex temperature plane. The former are obtained from rational approximations which are functions of the chemical potential at given values of the temperature; the latter are obtained from rational approximations which are functions of the temperature at given values of the chemical potential.

hep-lat↗

arXiv2024

Exploring the Critical Points in QCD with Multi-Point Padé and Machine Learning Techniques in (2+1)-flavor QCD

Using simulations at multiple imaginary chemical potentials for $(2+1)$-flavor QCD, we construct multi-point Padé approximants. We determine the singularties of the Padé approximants and demonstrate that they are consistent with the expected universal scaling behaviour of the Lee-Yang edge singularities. We also use a machine learning model, Masked Autoregressive Density Estimator (MADE), to estimate the density of the Lee-Yang edge singularities at each temperature. This ML model allows us to interpolate between the temperatures. Finally, we extrapolate to the QCD critical point using an appropriate scaling ansatz.

hep-lat↗

arXiv2022

Contribution to understanding the phase structure of strong interaction matter: Lee-Yang edge singularities from lattice QCD

We present a calculation of the net baryon number density as a function of imaginary baryon number chemical potential, obtained with highly improved staggered quarks (HISQ) at temporal lattice extent of $N_τ=4,6$. We construct various rational function approximations of the lattice data and discuss how poles in the complex plane can be determined from them. We compare our results of the singularities in the chemical potential plane to the theoretically expected positions of the Lee-Yang edge singularity in the vicinity of the Roberge-Weiss and chiral phase transitions. We find a temperature scaling that is in accordance with the expected power law behavior.

hep-lat↗

arXiv2021

Net-baryon number fluctuations

The appearance of large, none-Gaussian cumulants of the baryon number distribution is commonly discussed as a signal for the QCD critical point. We review the status of the Taylor expansion of cumulant ratios of baryon number fluctuations along the freeze-out line and also compare QCD results with the corresponding proton number fluctuations as measured by the STAR Collaboration at RHIC. To further constrain the location of a possible QCD critical point we discuss poles of the baryon number fluctuations in the complex plane. Here we use not only the Taylor coefficients obtained at zero chemical potential but perform also calculations of Taylor expansion coefficients of the pressure at purely imaginary chemical potentials.

hep-lat↗