Credit: SciTechDaily.comThe shift from a slowing down expansion routine (in the radiation- and matter-dominated era) to an accelerating expansion regime (in the dark energy-dominated age) resembles a thermodynamic phase shift, according to a short article in Results in Physics by scientists connected with São Paulo State University.The idea that the Universe is expanding dates from nearly a century earlier. Hubble observed that the redshift in the electro-magnetic spectrum of the light gotten from celestial objects was straight proportional to their distance from Earth, which indicated that bodies further away from Earth were moving away faster and the universe must be expanding.Discovery of Accelerating ExpansionA surprising brand-new active ingredient was included to the model in 1998 when observations of really distant supernovae by the Supernova Cosmology Project and the High-Z Supernova Search Team showed that the Universe is accelerating as it broadens, rather than being slowed down by gravitational forces, as had been expected. In 2010, Souza and 2 German collaborators revealed that the very same thing takes place near a finite-temperature crucial point.Recent Research Using the Grüneisen ParameterNow Souza and fellow researchers at UNESP have actually utilized the Grüneisen parameter to describe intricate aspects of the expansion of the Universe in a post published in the journal Results in Physics, presenting part of the PhD research of very first author Lucas Squillante, currently a postdoctoral fellow under Souzas supervision. The Mie– Grüneisen equation of state relates to temperature level, volume and pressure, and is frequently used to identify the pressure in a shock-compressed solid.Thermodynamics and the Anisotropic Expansion of the UniverseThe authors show, using the Grüneisen parameter, that constant cooling of the Universe is associated with a barocaloric impact that relates pressure and temperature and happens owing to adiabatic growth of the Universe. “We reveal that the Grüneisen specification is naturally embodied in the energy– momentum stress tensor in Einsteins well-known field equations, opening up a novel method to examine anisotropic effects associated with the growth of the Universe.
Researchers have actually made use of the Grüneisen parameter in studying the universes expansion, linking thermodynamics with cosmology. Their findings recommend deep spaces continuous cooling is connected to its adiabatic expansion, and the possible irregularity of the cosmological consistent obstacles standard models. Credit: SciTechDaily.comThe shift from a slowing down growth program (in the radiation- and matter-dominated era) to a speeding up expansion routine (in the dark energy-dominated age) resembles a thermodynamic phase shift, according to a post in Results in Physics by researchers connected with São Paulo State University.The concept that deep space is broadening dates from almost a century earlier. It was initially put forward by Belgian cosmologist Georges Lemaître (1894-1966) in 1927 and verified observationally by American astronomer Edwin Hubble (1889-1953) 2 years later. Hubble observed that the redshift in the electro-magnetic spectrum of the light gotten from celestial objects was straight proportional to their range from Earth, which implied that bodies farther away from Earth were moving away much faster and deep space needs to be expanding.Discovery of Accelerating ExpansionA surprising new component was added to the model in 1998 when observations of really distant supernovae by the Supernova Cosmology Project and the High-Z Supernova Search Team revealed that the Universe is accelerating as it expands, instead of being slowed down by gravitational forces, as had been supposed. This discovery caused the principle of dark energy, which is believed to account for more than 68% of all the energy in the currently observable Universe, while dark matter and common matter account for about 27% and 5% respectively.Representations of universe periods– (a) radiation, (b) matter, (c) dark energy– with the particular values of the formula of state ω = Γeff, where Γeff is the effective Grüneisen parameter. As dark energy ends up being dominant, Γeff changes indication and replicates a stage transition in condensed matter physics. Credit: Results in PhysicsApplication of Thermodynamics in Cosmology”Measurements of redshift recommend that the accelerating growth is adiabatic [without heat transfer] and anisotropic [differing in magnitude when measured in different directions],” said Mariano de Souza, a teacher in the Department of Physics at São Paulo State University (UNESP) in Rio Claro, Brazil. “Fundamental concepts in thermodynamics allow us to presume that adiabatic growth is always accompanied by cooling due to the barocaloric effect [pressure-induced thermal modification], which is quantified by the Grüneisen ratio [Γ, gamma]”In 1908, German physicist Eduard August Grüneisen (1877-1949) proposed a mathematical expression for Γeff, the efficient Grüneisen parameter, an important quantity in geophysics that typically occurs in equations explaining the thermoelastic behavior of material. It integrates 3 physical residential or commercial properties: expansion coefficient, particular heat, and isothermal compressibility. Practically a century later on, in 2003, Lijun Zhu and collaborators showed that a particular part of the Grüneisen criterion called the Grüneisen ratio, specified as the ratio of thermal expansion to specific heat, increases significantly in the area of a quantum critical point owing to the build-up of entropy. In 2010, Souza and two German partners revealed that the same thing takes place near a finite-temperature vital point.Recent Research Using the Grüneisen ParameterNow Souza and fellow researchers at UNESP have utilized the Grüneisen specification to explain detailed aspects of the expansion of deep space in an article released in the journal Results in Physics, presenting part of the PhD research study of first author Lucas Squillante, presently a postdoctoral fellow under Souzas guidance.”The characteristics associated with the expansion of deep space are typically designed as a perfect fluid whose equation of state is ω = p/ ρ, where ω [omega] is the equation of state specification, p is pressure, and ρ [rho] is energy density. ω is extensively used, its physical meaning had not yet been properly gone over. It was dealt with as simply a continuous for each age of the Universe. One of the essential outcomes of our research is the recognition of ω with the efficient Grüneisen criterion by ways of the Mie-Grüneisen equation of state,” Souza said. The Mie– Grüneisen equation of state relates to pressure, volume and temperature, and is typically utilized to determine the pressure in a shock-compressed solid.Thermodynamics and the Anisotropic Expansion of the UniverseThe authors show, using the Grüneisen specification, that continuous cooling of deep space is associated with a barocaloric effect that relates pressure and temperature level and takes place owing to adiabatic growth of the Universe. On this basis, they propose that the Grüneisen parameter is time-dependent in the dark energy-dominated era (the present universe age). One of the interesting elements of this research is its use of thermodynamics and solid-state physics ideas such as tension and pressure to explain the anisotropic growth of deep space. “We show that the Grüneisen specification is naturally embodied in the energy– momentum tension tensor in Einsteins popular field formulas, opening an unique method to examine anisotropic effects related to the expansion of deep space. These dont rule out the possibility of a Big Rip,” Souza said.The Big Rip hypothesis, first put forward in 2003 in a post published in Physical Review Letters, posits that if the quantity of dark energy suffices to accelerate the growth of deep space beyond a crucial velocity, this could tear the “material” of space-time and rip apart the Universe.Dark Energy and Theoretical Implications”Also in the viewpoint of the Grüneisen parameter, we opinion that the shift from a slowing down expansion regime [in the radiation and matter-dominated ages] to an accelerating expansion routine [in the dark energy-dominated era] looks like a thermodynamic phase shift. This is because Γeff changes indication when the growth changes from slowing down to accelerating. The indication change looks like the normal signature of phase shifts in condensed matter physics,” Souza said.Dark energy is often connected with the cosmological constant Λ [lambda], originally introduced by Einstein in 1917 as a repulsive force needed to keep deep space in static equilibrium. Einstein later on declined the concept, according to some accounts. It was fixed up when the expansion of deep space was found to be speeding up rather of decelerating. The hegemonic design, called Λ-CMD (Lambda-Cold Dark Matter), gives the cosmological constant a fixed value. That is, it presumes that the density of dark energy remains constant as the Universe expands. Nevertheless, other designs presume that the density of dark energy, and for this reason Λ, vary gradually.”Assigning a fixed value to lambda means also appointing a fixed value to omega, but acknowledgment of ω as the reliable Grüneisen parameter allows us to infer time reliance for ω as the Universe broadens in the dark energy-dominated period. This straight involves time dependency for Λ, or the universal gravitation continuous,” Souza said.The study could lead to important advancements insofar as it manages a peek of a novel analysis of the expansion of deep space in regards to thermodynamics and condensed matter physics.Reference: “Exploring the expansion of deep space using the Grüneisen parameter” by Lucas Squillante, Gabriel O. Gomes, Isys F. Mello, Guilherme Nogueira, Antonio C. Seridonio, Roberto E. Lagos-Monaco and Mariano de Souza, 17 January 2024, Results in Physics.DOI: 10.1016/ j.rinp.2024.107344 Besides Souza and Squillante, the other co-authors of the post are Antonio Seridonio (UNESP Ilha Solteira), Roberto Lagos-Monaco (UNESP Rio Claro), Gabriel Gomes (Institute of Astronomy, Geophysics and Atmospheric Sciences, University of São Paulo, IAG-USP), Guilherme Nogueira (UNESP Rio Claro), and PhD prospect Isys Mello, supervised by Souza.The study was supported by FAPESP via two tasks (11/22050 -4 and 18/09413 -0).