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By pressure demagnetization, take iron as an example, we mean either that, given an external magnetic field under a certain temperature, the magnetization becomes weaker as the pressure increases, which can be referred to as pressure demagnetization during magnetization, or that when external field is dropped to zero, the iron has residual magnetization or remanence, and the residual magnetization becomes weaker as the pressure increases as well, which can be referred to as pressure demagnetization in remanence. In order to account for the pressure demagnetization, we demonstrate that, though magnetic work has two equivalent forms in electromagnetism, only one form is proper in thermodynamics in general.

Abstract The classical and quantum dynamics of particles constrained on a right helicoid is discussed via Dirac approach. We show how the uncertainty in measurement for observables of maximally entangled system is affected by the total number of constrained particles $$\sigma $$ σ , external magnetic field $$\vec {\mathcal {B}}$$ B → ; as well as by geometric parameters like the pitch $$\rho $$ ρ and the radial position of particles. In doing so we also highlight numeric bounds on the external field strengths to tune both intraparticle and bipartite entanglement and we remark that the bipartite entanglement is more robust to changes in the fields than the intraparticle entanglement, in this framework. We also highlight specific parameter regimes which lead the uncertainty (in measurement) to achieve respective parameter independence and, for a particular subset of commutation relations, the system remains confined in the quantum regime even in the limit $$\sigma \rightarrow \infty $$ σ → ∞ . It is observed that the uncertainties are strongly influenced by the geometric parameters e.g., $$\rho $$ ρ , and the strength of bipartite as well as intraparticle entanglement might be controllable through $$\rho $$ ρ . The energy equation for this setup is obtained and the additional terms are discussed which arise due to quantum correlations, orbit–orbit interaction and the normal Zeeman effect, which leads to the splitting of the energy level into 11 non-degenerate levels. Finally we comment that, a linkage of this phenomenology with Aharonov–Bohm like effect might be possible by strictly confining $$\vec {\mathcal {B}}$$ B → along the central axis of the helicoid.

Critical exponent γ ⪰ 1.1 characterizes the behavior of the mechanical compressibility of a real fluid when the temperature approaches the critical one. It results in zero Gaussian curvature of the local shape of the critical point on the thermodynamic equation of state surface, which imposes a new constraint upon the construction of the potential equation of state of the real fluid from the empirical data. All known empirical equations of the state suffer from a weakness that the Gaussian curvature of the critical point is negative definite instead of zero.