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Volume comparison theorems for manifolds with radial curvature bounded

Jing Mao (2016)

Czechoslovak Mathematical Journal

In this paper, for complete Riemannian manifolds with radial Ricci or sectional curvature bounded from below or above, respectively, with respect to some point, we prove several volume comparison theorems, which can be seen as extensions of already existing results. In fact, under this radial curvature assumption, the model space is the spherically symmetric manifold, which is also called the generalized space form, determined by the bound of the radial curvature, and moreover, volume comparisons...

Volume ratios in L p -spaces

Yehoram Gordon, Marius Junge (1999)

Studia Mathematica

There exists an absolute constant c 0 such that for any n-dimensional Banach space E there exists a k-dimensional subspace F ⊂ E with k≤ n/2 such that i n f e l l i p s o i d ε B E ( v o l ( B E ) / v o l ( ε ) ) 1 / n c 0 i n f z o n o i d Z B F ( v o l ( B F ) / v o l ( Z ) ) 1 / k . The concept of volume ratio with respect to p -spaces is used to prove the following distance estimate for 2 q p < : s u p F p , d i m F = n i n f G L q , d i m G = n d ( F , G ) c p q n ( q / 2 ) ( 1 / q - 1 / p ) .

Volume thresholds for Gaussian and spherical random polytopes and their duals

Peter Pivovarov (2007)

Studia Mathematica

Let g be a Gaussian random vector in ℝⁿ. Let N = N(n) be a positive integer and let K N be the convex hull of N independent copies of g. Fix R > 0 and consider the ratio of volumes V N : = v o l ( K N R B ) / v o l ( R B ) . For a large range of R = R(n), we establish a sharp threshold for N, above which V N 1 as n → ∞, and below which V N 0 as n → ∞. We also consider the case when K N is generated by independent random vectors distributed uniformly on the Euclidean sphere. In this case, similar threshold results are proved for both R ∈ (0,1) and...

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