Epidemics, the Ising-model and percolation theory: A comprehensive review focused on Covid-19.

We revisit well-established concepts of epidemiology, the Ising-model, and percolation theory. Also, we employ a spin = 1/2 Ising-like model and a (logistic) Fermi-Dirac-like function to describe the spread of Covid-19. Our analysis show that: () in many cases the epidemic curve can be described by a Gaussian-type function; () the temporal evolution of the accumulative number of infections and fatalities follow a logistic function; () the key role played by the quarantine to block the spread of Covid-19 in terms of an interacting parameter between people.

Unveiling the Physics of the Mutual Interactions in Paramagnets.

In real paramagnets, there is always a subtle many-body contribution to the system's energy, which can be regarded as a small effective local magnetic field (B). Usually, it is neglected, since it is very small when compared with thermal fluctuations and/or external magnetic fields (B). Nevertheless, as both the temperature (T) → 0 K and B → 0 T, such many-body contributions become ubiquitous.

Enhanced Grüneisen Parameter in Supercooled Water.

We use the recently-proposed compressible cell Ising-like model to estimate the ratio between thermal expansivity and specific heat (the Grüneisen parameter Γ) in supercooled water. Near the critical pressure and temperature, Γ becomes significantly sensitive to thermal fluctuations of the order-parameter, a characteristic behavior of pressure-induced critical points. Such enhancement of Γ indicates that two energy scales are governing the system, namely the coexistence of high- and low-density liquids, which become indistinguishable at the critical point in the supercooled phase.