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Currently, a method has been developed for the cosmological inflation model with a single scalar field to calculate cosmological parameters such as the power spectrum of scalar and tensor perturbations, their spectral indices, and the…

General Relativity and Quantum Cosmology · Physics 2025-01-06 Katerina Bolshakova , Sergey Chervon

Let f be a smooth map between unit spheres of possibly different dimensions. We prove the global existence and convergence of the mean curvature flow of the graph of f under various conditions. A corollary is that any area-decreasing map…

Differential Geometry · Mathematics 2011-04-19 Mao-Pei Tsui , Mu-Tao Wang

We consider a class of anisotropic curvature flows called a crystalline curvature flow. We present a survey on this class of flows with special emphasis on the well-posedness of its initial value problem.

Analysis of PDEs · Mathematics 2021-12-13 Yoshikazu Giga , Norbert Požár

In this paper we will discuss how one may be able to use mean curvature flow to tackle some of the central problems in topology in 4-dimensions. We will be concerned with smooth closed 4-manifolds that can be smoothly embedded as a…

Differential Geometry · Mathematics 2012-08-30 Tobias Holck Colding , William P. Minicozzi , Erik Kjaer Pedersen

We review the study of inhomogeneous perturbations about a homogeneous and isotropic background cosmology. We adopt a coordinate based approach, but give geometrical interpretations of metric perturbations in terms of the expansion, shear…

Astrophysics · Physics 2010-04-23 Karim A. Malik , David Wands

We investigate how various inflationary and bouncing cosmologies can be realized by imperfect fluids with a generalized equation of state, in the context of both classical and loop quantum cosmology. With regards to the inflationary…

General Relativity and Quantum Cosmology · Physics 2017-09-06 V. K. Oikonomou

We revisit how super-Hubble cosmological fluctuations induce, at any time in the cosmic history, a non-vanishing spatial curvature of the local background metric. The random nature of these fluctuations promotes the curvature density…

Cosmology and Nongalactic Astrophysics · Physics 2023-12-06 Baptiste Blachier , Pierre Auclair , Christophe Ringeval , Vincent Vennin

In clusters of galaxies, the specific entropy of intracluster plasma increases outwards. Nevertheless, a number of recent studies have shown that the intracluster medium is subject to buoyancy instabilities due to the effects of cosmic rays…

Astrophysics · Physics 2009-11-13 Yann Rasera , Benjamin Chandran

In this paper we study smooth solutions to a fractional mean curvature flow equation. We establish a comparison principle and consequences such as uniqueness and finite extinction time for compact solutions. We also establish evolutions…

Analysis of PDEs · Mathematics 2019-04-01 Mariel Sáez , Enrico Valdinoci

We consider a diffused interface version of the volume-preserving mean curvature flow in the Euclidean space, and prove, in every dimension and under natural assumptions on the initial datum, exponential convergence towards single "diffused…

Analysis of PDEs · Mathematics 2024-07-29 Matteo Bonforte , Francesco Maggi , Daniel Restrepo

We consider the evolution of a $n$-dimensional convex hypersurface in the euclidean space under mean curvature flow with densities $e^{\varepsilon \frac12 n\mu^2 |x|^2}$, $\varepsilon =\pm 1$, and completely determine it depending on the…

Differential Geometry · Mathematics 2009-12-23 Alexander A. Borisenko , Vicente Miquel

We find initial data for numerical relativity simulations of inhomogeneous cosmologies. This involves treating an exceptional case of the general relativity constraint equations. We devise analytic and numerical methods to treat this…

General Relativity and Quantum Cosmology · Physics 2020-08-19 David Garfinkle , Lawrence Mead

We employ three different methods to prove the following result on prescribed scalar curvature plus mean curvature problem: Let $(M^n,g_0)$ be a $n$-dimensional smooth compact manifold with boundary, where $n \geq 3$, assume the conformal…

Differential Geometry · Mathematics 2018-04-20 Xuezhang Chen , Pak Tung Ho , Liming Sun

The central object of study of this thesis is inverse mean curvature vector flow of two-dimensional surfaces in four-dimensional spacetimes. Being a system of forward-backward parabolic PDEs, inverse mean curvature vector flow equation…

Differential Geometry · Mathematics 2015-08-18 Hangjun Xu

In this paper we investigate the convergence for the mean curvature flow of closed submanifolds with arbitrary codimension in space forms. Particularly, we prove that the mean curvature flow deforms a closed submanifold satisfying a…

Differential Geometry · Mathematics 2011-05-31 Kefeng Liu , Hongwei Xu , Fei Ye , Entao Zhao

Measurements of CMB anisotropy and, more recently, polarization have played a very important role allowing precise determination of various parameters of the `standard' cosmological model. The expectation of the paradigm of inflation and…

Astrophysics · Physics 2008-11-26 Tarun Souradeep

We find a new monotone increasing quantity along smooth solutions to the inverse mean curvature flow in $\mathbb R^n$. As an application, we derive a sharp geometric inequality for mean convex, star-shaped hypersurfaces which relates the…

Differential Geometry · Mathematics 2016-01-20 Kwok-Kun Kwong , Pengzi Miao

In these lectures I review the standard hot big-bang cosmology, emphasizing its successes, its shortcomings, and its major challenges-developing a detailed understanding of the formation of structure in the Universe and identifying the…

Astrophysics · Physics 2014-10-13 Michael S. Turner

Average properties of general inhomogeneous cosmological models are discussed in the Newtonian framework. It is shown under which circumstances the average flow reduces to a member of the standard Friedmann--Lema\^\i tre cosmologies.…

Astrophysics · Physics 2008-02-03 T. Buchert

We study the mean curvature flow of smooth $m$-dimensional compact submanifolds with quadratic pinching in the Riemannian manifold $\mathbb{C}P^n$. Our main focus is on the case of high codimension, $k\geq 2$. We establish a codimension…

Differential Geometry · Mathematics 2023-11-16 Artemis A. Vogiatzi
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