The sum of squared logarithms inequality in n dimensions

For nNn\in\mathbb{N}, let λ1,λ2,,λn,μ1,μ2,,μnR+\lambda_1,\lambda_2,\ldots,\lambda_n,\mu_1,\mu_2,\ldots,\mu_n\in\mathbb{R}_+, and let

ek(X1,X2,,Xn)=1j1<j2<<jknXj1Xj2Xjk,k=1,,n,e_k(X_1,X_2,\ldots,X_n)=\sum_{1\leq j_1<j_2<\cdots<j_k\leq n}X_{j_1}X_{j_2}\cdots X_{j_k},\qquad k=1,\ldots,n,

be the elementary symmetric polynomials. The sum of squared logarithms inequality. If

ek(λ1,λ2,,λn)ek(μ1,μ2,,μn),k=1,,n1,e_k(\lambda_1,\lambda_2,\ldots,\lambda_n)\leq e_k(\mu_1,\mu_2,\ldots,\mu_n),\qquad k=1,\ldots,n-1,

and

en(λ1,λ2,,λn)=en(μ1,μ2,,μn),e_n(\lambda_1,\lambda_2,\ldots,\lambda_n)=e_n(\mu_1,\mu_2,\ldots,\mu_n),

then

k=1nlog2λkk=1nlog2μk.\sum_{k=1}^n\log^2\lambda_k\leq\sum_{k=1}^n\log^2\mu_k.

The inequality extends the corresponding results established in dimensions two and three and is relevant to the analysis of logarithmic strain energies and their convexity properties. The general nn-dimensional case is presented as a conjecture, while the two- and three-dimensional cases are known.

Sources & referencesView supporting material

Primary source

Patrizio Neff, Johannes Lankeit, Ionel-Dumitrel Ghiba, Robert Martin and David Steigmann, “The exponentiated Hencky-logarithmic strain energy. Part II: Coercivity, planar polyconvexity and existence of minimizers”, arXiv:1408.4430 (2014).

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