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We use the mean-field dynamo equations to show that an incoherent alpha effect in mirror-symmetric turbulence in a shearing flow can generate a large scale, coherent magnetic field. We illustrate this effect with simulations of a few simple…

天体物理学 · 物理学 2015-06-24 Ethan T. Vishniac , Axel Brandenburg

In this work, which follows a series of studies on the higher-dimensional steady state universe idea and prepared for Professor Tekin Dereli's Festschrift, we show the influence of the dynamical internal (unobservable) space on the…

广义相对论与量子宇宙学 · 物理学 2022-02-23 Ozgur Akarsu , Tekin Dereli , Nihan Katirci

A weak fluctuating magnetic field embedded into a turbulent conducting medium grows exponentially while its characteristic scale decays. In the ISM and protogalactic plasmas, the magnetic Pr is very large, so a broad spectrum of growing…

天体物理学 · 物理学 2008-11-26 Alexander Schekochihin , Steven Cowley , Jason Maron , Leonid Malyshkin

We study a new approach to generally covariant quantum mechanics applied in the case of an FLRW cosmological background. For positive spatial curvature we find a discrete series of solutions of the Klein-Gordon equation that can reasonably…

广义相对论与量子宇宙学 · 物理学 2025-11-13 Edwin Beggs , Shahn Majid

We investigate the Lagrangian mechanism of the kinematic ``fluctuation'' magnetic dynamo in turbulent plasma flow at small magnetic Prandtl numbers. The combined effect of turbulent advection and plasma resistivity is to carry infinitely…

等离子体物理 · 物理学 2015-05-13 Gregory L. Eyink , Antonio F. Neto

It is shown, that the saturated $\alpha$-effect taken from the nonlinear dynamo equations for the thin disk can still produce exponentially growing magnetic field in the case, when this field does not feed back on the $\alpha$. For negative…

流体动力学 · 物理学 2015-05-18 M. Reshetnyak

Most of the theoretical results on the kinematic amplification of small-scale magnetic fluctuations by turbulence have been confined to the model of white-noise-like advecting turbulent velocity field. In this work, the statistics of the…

天体物理学 · 物理学 2009-10-31 Alexander Schekochihin , Russell Kulsrud

A special class of conformal gravity theories is proposed to solve the long standing problem of the fine-tuned cosmological constant. In the proposed model time evolution of the inflaton field leaves behind a nearly vanishing, but finite…

高能物理 - 唯象学 · 物理学 2022-04-25 M. Yoshimura

Based on the new findings on the turbulent dynamo in \citet{XL16}, we examine the magnetic field amplification in the context of supernova remnants. Due to the strong ion-neutral collisional damping in the weakly-ionized interstellar…

高能天体物理现象 · 物理学 2017-12-13 Siyao Xu , Alex Lazarian

We apply the new dynamics of 3-space to cosmology by deriving a Hubble expansion solution. This dynamics involves two constants; G and alpha - the fine structure constant. This solution gives an excellent parameter-free fit to the recent…

综合物理 · 物理学 2007-06-27 Reginald T Cahill

Statistical mechanics of 1D multivalent Coulomb gas may be mapped onto non-Hermitian quantum mechanics. We use this example to develop instanton calculus on Riemann surfaces. Borrowing from the formalism developed in the context of…

统计力学 · 物理学 2015-06-15 Tobias Gulden , Michael Janas , Peter Koroteev , Alex Kamenev

Magnetic fields of low-mass stars and planets are thought to originate from self-excited dynamo action in their convective interiors. Observations reveal a variety of field topologies ranging from large-scale, axial dipole to more…

太阳与恒星天体物理 · 物理学 2015-06-04 Martin Schrinner , Ludovic Petitdemange , Emmanuel Dormy

We consider general curvature-invariant modifications of the Einstein-Hilbert action that become important only in regions of extremely low space-time curvature. We investigate the far future evolution of the universe in such models,…

During the first 40 s after their birth, proto-neutron stars are expected to be subject to at least two types of instability: the convective instability and the neutron-finger one. Both instabilities involve convective motions and hence can…

天体物理学 · 物理学 2009-06-23 L. Naso , L. Rezzolla , A. Bonanno , L. Paternò

We have extended our previous mean-field galactic dynamo model which included algebraic and dynamic alpha nonlinearities (Kleeorin et al., A&A, v. 387, 453, 2002), to include also a quenching of turbulent diffusivity. We readily obtain…

天体物理学 · 物理学 2014-10-13 N. Kleeorin , D. Moss , I. Rogachevskii , D. Sokoloff

We have performed the dynamical system analysis to obtain the critical point in which, the value of the geometric and dynamical parameters satisfy the late-time cosmic behavior of the Universe. At the outset, the modified Friedmann…

广义相对论与量子宇宙学 · 物理学 2025-10-30 Rahul Bhagat , B. Mishra

It was found that the model with interaction between cold dark matter (CDM) and dark energy (DE) proportional to the energy density of CDM $\rho_m$ and constant equation of state of DE $w_d$ suffered from instabilities of the density…

广义相对论与量子宇宙学 · 物理学 2015-05-30 Cheng-Yi Sun , Yu Song , Rui-Hong Yue

We show that the current accelerated expansion of the Universe can be explained without resorting to dark energy. Models of generalized modified gravity, with inverse powers of the curvature can have late time accelerating attractors…

天体物理学 · 物理学 2008-11-26 Olga Mena , Jose Santiago , Jochen Weller

By using the effective field theory approach, we investigate the role of initial condition for the dark energy or modified gravity models. In details, we consider the constant and linear parametrization of the effective Newton constant…

宇宙学与河外天体物理 · 物理学 2018-01-10 Xue-Wen Liu , Bin Hu , Yi Zhang

Recent advances in mean-field theory are reviewed and applications to the Sun, late-type stars, accretion disks, galaxies, and the early Universe are discussed. We focus particularly on aspects of spatio-temporal nonlocality, which is one…

流体动力学 · 物理学 2019-01-14 Axel Brandenburg