I review Stanley Mandelstams many contributions to particle physics, quantum field theory and string theory covering the years 1955 through 1980. His more recent work will be reviewed by Nathan Berkovits. This is my contribution to the Memorial Volume for Stanley Mandelstam (World Scientific, 2017).
Selected events of the scientific biography of Wojtek Dziembowski are briefly described, and several related photos are presented. The full version of the presentation is available at the IAU Symposium 301 webpage.
We highlight some of the interesting properties of a new and finite, exact family of solutions of 1 + 1 dimensional perfect fluid relativistic hydrodynamics. After reviewing the main properties of this family of solutions, we present the formulas that connect it to the measured rapidity and pseudo-rapidity densities and illustrate the results with fits to p+p collisions at 8 TeV and Pb+Pb collisions at $sqrt{s_{NN}} = 5.02 $ TeV.
We analyse the symmetries of a class of A-type little string theories that are engineered by $N$ parallel M5-branes with M2-branes stretched between them. This paper deals with the so-called reduced free energy, which only receives contributions from the subset of the BPS states that carry the same charges under all the Cartan generators of the underlying gauge algebra. We argue (and check explicitly in a number of examples) that the former is invariant under the paramodular group $Sigma_Nsubset Sp(4,mathbb{Q})$, which gets extended to a subgroup of $Sp(4,mathbb{R})$ in the Nekrasov-Shatashvili-limit. This extension agrees with the observation made in arXiv:1706.04425 that these BPS states form a symmetric orbifold CFT. Furthermore, we argue that $Sigma_N$ (along with other symmetries) places strong constraints on the BPS counting function that governs the intersection between the M5- and M2-branes.
Exclusive photoproduction cross sections have been measured for the process $gamma p rightarrow ppi^0(e^+e^-(gamma))$ with the Dalitz decay final state using tagged photon energies in the range of $E_{gamma} = 1.275-5.425$ GeV. The complete angular distribution of the final state $pi^0$, for the entire photon energy range up to large values of $t$ and $u$, has been measured for the first time. The data obtained show that the cross section $dsigma/dt$, at mid to large angles, decreases with energy as $s^{-6.89pm 0.26} $. This is in agreement with the perturbative QCD quark counting rule prediction of $s^{-7} $. Paradoxically, the size of angular distribution of measured cross sections is greatly underestimated by the QCD based Generalized Parton Distribution mechanism at highest available invariant energy $s=11$ GeV$^2$. At the same time, the Regge exchange based models for $pi^0$ photoproduction are more consistent with experimental data.
This paper is the second part of a previous paper (Marquet, 2019) dealing with the need to define the entropy with an absolute way, by using the third law of thermodynamics. In this second part it is shown that there is a need and interest to define a potential temperature which is a synonym of the moist-air absolute entropy, with several possible novel applications to study meteorology and climate processes.