Papers by Winfried Zimdahl
Hydrodynamic Fluctuations in Cosmology
grg, Jul 1, 1989
Nucleation and Atmospheric Aerosols, 2012
Any non-gravitational coupling between dark matter and dark energy modifies the cosmological dyna... more Any non-gravitational coupling between dark matter and dark energy modifies the cosmological dynamics. Interactions in the dark sector are considered to be relevant to address the coincidence problem. Moreover, in various models the observed accelerated expansion of the Universe is a pure interaction phenomenon. Here we review recent approaches in which a coupling between both dark components is crucial for the evolution of the Universe.
The Luttinger method in the theory of thermomagnetic phenomena
JETP, Dec 1, 1974
arXiv (Cornell University), Oct 3, 2021
This paper tries to present a simple picture of several aspects of the mode structure in relativi... more This paper tries to present a simple picture of several aspects of the mode structure in relativistic non-equilibrium thermodynamics. Its pedagogical focus is on the relation between long-wavelength perturbation modes of the causal Müller-Israel-Stewart (MIS) theory and those of the traditional Eckart theory. Principally, this issue was clarified in a series of papers by Hiscock and Lindblom (see [8, 9, 10]). Here, I put together some essential features of this topic which do not require the entire formalism of the complete theory.
Cadernos de Astronomia, Feb 1, 2022
This paper tries to present a simple picture of several aspects of the mode structure in relativi... more This paper tries to present a simple picture of several aspects of the mode structure in relativistic non-equilibrium thermodynamics. Its pedagogical focus is on the relation between long-wavelength perturbation modes of the causal Müller-Israel-Stewart (MIS) theory and those of the traditional Eckart theory. Principally, this issue was clarified in a series of papers by Hiscock and Lindblom (see [8, 9, 10]). Here, I put together some essential features of this topic which do not require the entire formalism of the complete theory.
AIP Conference Proceedings, 2012
The creation of ultra-light dark particles in the late-time FLRW spacetime provides a cosmologica... more The creation of ultra-light dark particles in the late-time FLRW spacetime provides a cosmological model in accordance with precise observational tests. The matter creation backreaction implies in this context a vacuum energy density scaling linearly with the Hubble parameter H, which is consistent with the vacuum expectation value of the QCD condensate in a low-energy expanding spacetime. Both the cosmological constant and coincidence problems are alleviated in this scenario. We also explore the opposite, high energy limit of the particle creation process. We show that it leads to a non-singular primordial universe where an early inflationary era takes place, with natural reheating and exit. The generated primordial spectrum is scale invariant and, by supposing that inflation lasts for 60 e-folds, we obtain a scalar expectral index n ≈ 0.97.
Cadernos de Astronomia, Feb 1, 2022
Apresenta-se uma tradução do alemão, do artigo seminal de Alexander Friedmann publicado em 1922, ... more Apresenta-se uma tradução do alemão, do artigo seminal de Alexander Friedmann publicado em 1922, onde encontram-se as bases de um modelo cosmológico dinâmico.
Modelos de contrarreação cosmológica
Perturbações da matéria num modelo cosmológico com interações no setor escuro
Cosmology with Adiabatic Matter Creation
International Journal of Modern Physics D, Mar 1, 1994
The standard Friedmann-Lemaître-Robertson-Walker (FLRW) model is modified to include particle pro... more The standard Friedmann-Lemaître-Robertson-Walker (FLRW) model is modified to include particle production processes. The influence of these processes on the dynamics of the early Universe is investigated. We argue that a sufficiently high creation rate may give rise to an inflationary period. A stability analysis about this background yields growing energy density perturbations during the de Sitter stage.
arXiv (Cornell University), Jun 22, 2006
We demonstrate that a transition from decelerated to accelerated cosmic expansion arises as a pur... more We demonstrate that a transition from decelerated to accelerated cosmic expansion arises as a pure interaction phenomenon if pressureless dark matter is coupled to holographic dark energy whose infrared cutoff scale is set by the Hubble length. In a spatially flat universe the ratio of the energy densities of both components remains constant through this transition, while it is subject to slow variations for non-zero spatial curvature. The coincidence problem is dynamized and reformulated in terms of the interaction rate. An early matter era is recovered since for negligible interaction at high redshifts the dark energy itself behaves as matter. A simple model for this dynamics is shown to fit the SN Ia data. The constant background energy density ratio simplifies the perturbation analysis which is characterized by non-adiabatic features.
Cosmologia com interação no setor escuro do Universo
Interações no Setor Escuro do Universo
Perturbações bariônicas no modelo com decaimento do vácuo
Fluidos Ideais em Relatividade Geral e Cosmologia
Dark Matter and Dissipation
International Journal of Modern Physics D, Mar 1, 1994
The uncertainty about the current values of the observational parameters leaves ample room for a ... more The uncertainty about the current values of the observational parameters leaves ample room for a bulk dissipative stress on cosmic scales which, we argue, may be ascribed to the presence of dark matter. As a byproduct the constraint 2q0
Extensão do modelo LambdaCDM, baseada na teoria escalar-tensorial da gravitação
Universidade Federal do Espírito Santo, Aug 1, 2018
Dinâmica Cosmológica para Modelos com Interações Não-Lineares no Setor Escuro
Quando Gravitação e Cosmologia Destoam do Padrão : Testando MOND e modelos de unificação do setor escuro
Jose Plinio Baptista School of Cosmology (1. : 2012 : Anchieta, ES). Seminario realizado no perio... more Jose Plinio Baptista School of Cosmology (1. : 2012 : Anchieta, ES). Seminario realizado no periodo de 14 a 19 de outubro de 2012.
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Papers by Winfried Zimdahl