Averaging Generalized Scalar Field Cosmologies II: Locally Rotationally Symmetric Bianchi I and flat Friedmann-Lema\^itre-Robertson-Walker models

Scalar field cosmologies with a generalized harmonic potential and a matter fluid with a barotropic Equation of State (EoS) with barotropic index $\gamma$ for the Locally Rotationally Symmetric (LRS) Bianchi I and flat Friedmann-Lema\^itre-Robertson-Walker (FLRW) metrics are investigated. Methods from the theory of averaging of nonlinear dynamical systems are used to prove that time-dependent systems and their corresponding time-averaged versions have the same late-time dynamics. Therefore, the simplest time-averaged system determines the future asymptotic behavior. Depending on the values of $\gamma$, the late-time attractors of physical interests are flat quintessence dominated FLRW universe and Einstein-de Sitter solution. With this approach, the oscillations entering the system through the Klein-Gordon (KG) equation can be controlled and smoothed out as the Hubble parameter $H$ - acting as time-dependent perturbation parameter - tends monotonically to zero. Numerical simulations are presented as evidence of such behavior.Comment: Research Program Averaging Generalized Scalar Field Cosmologies, part II. 27 pages, 7 compound figures. Minor revision. References updated. Discussion improve

Averaging Generalized Scalar Field Cosmologies I: Locally Rotationally Symmetric Bianchi III and open Friedmann-Lema\^itre-Robertson-Walker models

Scalar field cosmologies with a generalized harmonic potential and a matter fluid with a barotropic Equation of State (EoS) with barotropic index $\gamma$ for Locally Rotationally Symmetric (LRS) Bianchi III metric and open Friedmann-Lema\^itre-Robertson-Walker (FLRW) metric are investigated. Methods from the theory of averaging of nonlinear dynamical systems are used to prove that time-dependent systems and their corresponding time-averaged versions have the same late-time dynamics. Therefore, simple time-averaged systems determine the future asymptotic behavior. Depending on values of barotropic index $\gamma$ late-time attractors of physical interests for LRS Bianchi III metric are Bianchi III flat spacetime, matter dominated FLRW universe (mimicking de Sitter, quintessence or zero acceleration solutions) and matter-curvature scaling solution. For open FLRW metric late-time attractors are a matter dominated FLRW universe and Milne solution. With this approach, oscillations entering nonlinear system through Klein-Gordon (KG) equation can be controlled and smoothed out as the Hubble factor $H$ - acting as a time-dependent perturbation parameter - tends monotonically to zero. Numerical simulations are presented as evidence of such behaviour.Comment: Research Program Averaging Generalized Scalar Field Cosmologies, part I. 48 pages, 24 compound figures. Minor revision. References adde

Averaging generalized scalar-field cosmologies III: Kantowski–Sachs and closed Friedmann–Lemaître–Robertson–Walker models

Scalar-field cosmologies with a generalized harmonic potential and matter with energy density $$\rho _m$$, pressure $$p_m$$, and barotropic equation of state (EoS) $$p_m=(\gamma -1)\rho _m, \; \gamma \in [0,2]$$ in Kantowski–Sachs (KS) and closed Friedmann–Lemaître–Robertson–Walker (FLRW) metrics are investigated. We use methods from non-linear dynamical systems theory and averaging theory considering a time-dependent perturbation function D. We define a regular dynamical system over a compact phase space, obtaining global results. That is, for KS metric the global late-time attractors of full and time-averaged systems are two anisotropic contracting solutions, which are non-flat locally rotationally symmetric (LRS) Kasner and Taub (flat LRS Kasner) for $$0\le \gamma \le 2$$, and flat FLRW matter-dominated universe if $$0\le \gamma \le \frac{2}{3}$$. For closed FLRW metric late-time attractors of full and averaged systems are a flat matter-dominated FLRW universe for $$0\le \gamma \le \frac{2}{3}$$ as in KS and Einstein–de Sitter solution for $$0\le \gamma <1$$. Therefore, a time-averaged system determines future asymptotics of the full system. Also, oscillations entering the system through Klein–Gordon (KG) equation can be controlled and smoothed out when D goes monotonically to zero, and incidentally for the whole D-range for KS and closed FLRW (if $$0\le \gamma < 1$$) too. However, for $$\gamma \ge 1$$ closed FLRW solutions of the full system depart from the solutions of the averaged system as D is large. Our results are supported by numerical simulations

Dalla Margherita all'Obelisco: arte fantastica italiana tra Roma e New York negli anni ’40 in Irene Brin Gaspero Del Corso e l’Obelisco

Prima dell'affermarsi di altre gallerie che fecero la storia dell'arte a Roma tra la fine degli anni '50 e l'inizio degli anni '70, la Galleria L'Obelisco (1946-1981) fu uno dei pochi luoghi nella Capitale a promuovere la ricerca artistica contemporanea con un'attività serrata, continua e sperimentale, aperta all'arte e al collezionismo italiani e stranieri. Sorta all'indomani della Liberazione, fu diretta da Gaspero del Corso e Irene Brin, influente interprete del più colto ed eclettico giornalismo di moda e protagonista del lancio internazionale del «made in Italy» dal dopoguerra in poi. Grazie al fine intuito, all'ampiezza di interessi, alla disponibilità verso il nuovo e al cóté mondano della coppia, la Galleria L'Obelisco non solo sostenne l'arte contemporanea presso intenditori, critici e artisti, ma si rivolse anche a un pubblico più vasto e variegato, innovando radicalmente le modalità espositive, comunicative e promozionali dell'arte all'insegna della contaminazione e del dialogo tra diversi ambiti della cultura. Il libro è la prima monografia sulla galleria romana: i contributi scientifici sui diversi aspetti della figura di Irene Brin e sull'attività de L'Obelisco sono affiancati da un ricco corredo fotografico, in parte inedito, e da regesti documentari e testimonianze, raccolte per l'occasione presso coloro che, a vario titolo, hanno vissuto quel pezzo fondamentale della storia dell'arte e della cultura del nostro paese