chemia: State of matter

Evidence: 49 • authority: 92

Spin effects in superfluidity, neutron matter, and neutron stars.. We review selected aspects of the interior physics of compact stars, focusing on the microscopic and macroscopic manifestations of spin, magnetic fields, and nucleonic superfluidity and superconductivity. Spin statistics of fermions allow quantum degeneracy pressure to determine the stability and global properties of neutron stars, whose structure depends sensitively on the strong interactions among baryons in dense matter. Using a generic metamodeling framework based on an expansion of the nuclear energy density around the isospin-symmetric and saturation-density limits, we highlight how various lesser-known terms in this e…

Evidence: 49 • authority: 72

Absolute zero is the theoretically coldest temperature, a state at which a system's internal energy, and in ideal cases entropy, reach their minimum values. The Kelvin scale is defined so that absolute zero is 0 Kelvin, equivalent to −273.15 °C on the Celsius scale, and −459.67 °F on the Fahrenheit scale. The Kelvin and Rankine temperature scales set their zero points at absolute zero by definition. This limit can be estimated by extrapolating the ideal gas law to the temperature at which the volume or pressure of a classical gas becomes zero. Although absolute zero can be approached, it cannot be reached. Some isentropic processes, such as adiabatic expansion, can lower the system's temper…

Evidence: 49 • authority: 72

In physics, a state of matter or phase of matter is one of the distinct forms in which matter can exist. Four states of matter are observable in everyday life: solid, liquid, gas, and plasma. Different states are distinguished by the ways the component particles (atoms, molecules, ions and electrons) are arranged, and how they behave collectively. In a solid, the particles are tightly packed and held in fixed positions, giving the material a definite shape and volume. In a liquid, the particles remain close together but can move past one another, allowing the substance to maintain a fixed volume while adapting to the shape of its container. In a gas, the particles are far apart and move fre…

Evidence: 44 • authority: 92

Detecting complex-energy braiding topology in a dissipative atomic simulator with transformer-based geometric tomography.. Machine learning (ML) is shaping our exploration of topological matter, whose existence is inherently tied to the geometry of quantum states or energy spectra. In non-Hermitian systems, distinctive spectral geometry can lead to topological braiding of complex-energy bands, yet directly probing this topology-geometry interplay remains challenging. Here, we introduce a Transformer-based ML framework to capture this interplay and experimentally demonstrate it in a dissipative cold-atom simulator. Using a Bose-Einstein condensate, we engineer tunable dissipative two-level s…

Evidence: 39 • authority: 72

In astrophysics, a gravastar (a blend word of "gravitational vacuum star") is an object hypothesized in a 2001 paper by Pawel O. Mazur and Emil Mottola as an alternative to the black hole theory. It has the usual black hole metric outside of the horizon, but de Sitter metric inside. A typical gravastar is as big as London, but weighing ten solar masses. On the horizon there is an ultra-thin, incredibly tight shell of entirely new, unique exotic matter. This solution to the Einstein equations is stable and has no singularities. Instead, a gravastar is filled either with dark energy or with vacuum energy, but also vacuum, only the inside one is 1044 times denser than the outside.

Evidence: 39 • authority: 72

Superfluid helium-4 (helium II or He-II) is the superfluid form of helium-4, the most common isotope of the element helium. The substance, which resembles other liquids such as helium I (conventional, non-superfluid liquid helium), flows without friction past any surface, which allows it to continue to circulate over obstructions and through pores in containers which hold it, subject only to its own inertia. The formation of the superfluid is a manifestation of the formation of a Bose–Einstein condensate of helium atoms. This condensation occurs in liquid helium-4 at a far higher temperature (2.17 K) than it does in helium-3 (2.5 mK) because each atom of helium-4 is a boson particle, by vir…

Evidence: 34 • authority: 72

Cold is the presence of low temperature, especially in the atmosphere. In common usage, cold is often a subjective perception. A lower bound to temperature is absolute zero, defined as 0.00 K on the Kelvin scale, an absolute thermodynamic temperature scale. This corresponds to −273.15 °C on the Celsius scale, −459.67 °F on the Fahrenheit scale, and 0.00 °R on the Rankine scale. Since temperature relates to the thermal energy held by an object or a sample of matter, which is the kinetic energy of the random motion of the particle constituents of matter, an object will have less thermal energy when it is colder and more when it is hotter. If it was possible to cool a system to absolute zero,…