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Search: All articles in the CJM digital archive with keyword embedding

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1. CJM Online first

Ostrovskii, Mikhail; Randrianantoanina, Beata
Metric spaces admitting low-distortion embeddings into all $n$-dimensional Banach spaces
For a fixed $K\gg 1$ and $n\in\mathbb{N}$, $n\gg 1$, we study metric spaces which admit embeddings with distortion $\le K$ into each $n$-dimensional Banach space. Classical examples include spaces embeddable into $\log n$-dimensional Euclidean spaces, and equilateral spaces. We prove that good embeddability properties are preserved under the operation of metric composition of metric spaces. In particular, we prove that $n$-point ultrametrics can be embedded with uniformly bounded distortions into arbitrary Banach spaces of dimension $\log n$. The main result of the paper is a new example of a family of finite metric spaces which are not metric compositions of classical examples and which do embed with uniformly bounded distortion into any Banach space of dimension $n$. This partially answers a question of G. Schechtman.

Keywords:basis constant, bilipschitz embedding, diamond graph, distortion, equilateral set, ultrametric
Categories:46B85, 05C12, 30L05, 46B15, 52A21

2. CJM 2015 (vol 67 pp. 1046)

Dubickas, Arturas; Sha, Min; Shparlinski, Igor
Explicit Form of Cassels' $p$-adic Embedding Theorem for Number Fields
In this paper, we mainly give a general explicit form of Cassels' $p$-adic embedding theorem for number fields. We also give its refined form in the case of cyclotomic fields. As a byproduct, given an irreducible polynomial $f$ over $\mathbb{Z}$, we give a general unconditional upper bound for the smallest prime number $p$ such that $f$ has a simple root modulo $p$.

Keywords:number field, $p$-adic embedding, height, polynomial, cyclotomic field
Categories:11R04, 11S85, 11G50, 11R09, 11R18

3. CJM 2014 (vol 67 pp. 810)

Elliott, George A.; Niu, Zhuang
All Irrational Extended Rotation Algebras are AF Algebras
Let $\theta\in[0, 1]$ be any irrational number. It is shown that the extended rotation algebra $\mathcal B_\theta$ introduced in a previous paper is always an AF algebra.

Keywords:irrational rotation algebra, extended irrational rotation algebra, AF-embedding

4. CJM 2010 (vol 63 pp. 436)

Mine, Kotaro; Sakai, Katsuro
Simplicial Complexes and Open Subsets of Non-Separable LF-Spaces
Let $F$ be a non-separable LF-space homeomorphic to the direct sum $\sum_{n\in\mathbb{N}} \ell_2(\tau_n)$, where $\aleph_0 < \tau_1 < \tau_2 < \cdots$. It is proved that every open subset $U$ of $F$ is homeomorphic to the product $|K| \times F$ for some locally finite-dimensional simplicial complex $K$ such that every vertex $v \in K^{(0)}$ has the star $\operatorname{St}(v,K)$ with $\operatorname{card} \operatorname{St}(v,K)^{(0)} < \tau = \sup\tau_n$ (and $\operatorname{card} K^{(0)} \le \tau$), and, conversely, if $K$ is such a simplicial complex, then the product $|K| \times F$ can be embedded in $F$ as an open set, where $|K|$ is the polyhedron of $K$ with the metric topology.

Keywords:LF-space, open set, simplicial complex, metric topology, locally finite-dimensional, star, small box product, ANR, $\ell_2(\tau)$, $\ell_2(\tau)$-manifold, open embedding, $\sum_{i\in\mathbb{N}}\ell_2(\tau_i)$
Categories:57N20, 46A13, 46T05, 57N17, 57Q05, 57Q40

5. CJM 2008 (vol 60 pp. 961)

Abrescia, Silvia
About the Defectivity of Certain Segre--Veronese Varieties
We study the regularity of the higher secant varieties of $\PP^1\times \PP^n$, embedded with divisors of type $(d,2)$ and $(d,3)$. We produce, for the highest defective cases, a ``determinantal'' equation of the secant variety. As a corollary, we prove that the Veronese triple embedding of $\PP^n$ is not Grassmann defective.

Keywords:Waring problem, Segre--Veronese embedding, secant variety, Grassmann defectivity
Categories:14N15, 14N05, 14M12

6. CJM 2004 (vol 56 pp. 1068)

Steinbach, Anja; Van Maldeghem, Hendrik
Regular Embeddings of Generalized Hexagons
We classify the generalized hexagons which are laxly embedded in projective space such that the embedding is flat and polarized. Besides the standard examples related to the hexagons defined over the algebraic groups of type $\ssG_2$, $^3\ssD_4$ and $^6\ssD_4$ (and occurring in projective dimensions $5,6,7$), we find new examples in unbounded dimension related to the mixed groups of type $\ssG_2$.

Keywords:Moufang generalized hexagons, embeddings, mixed hexagons, classical, hexagons
Categories:51E12, 51A45

7. CJM 1999 (vol 51 pp. 585)

Mansfield, R.; Movahedi-Lankarani, H.; Wells, R.
Smooth Finite Dimensional Embeddings
We give necessary and sufficient conditions for a norm-compact subset of a Hilbert space to admit a $C^1$ embedding into a finite dimensional Euclidean space. Using quasibundles, we prove a structure theorem saying that the stratum of $n$-dimensional points is contained in an $n$-dimensional $C^1$ submanifold of the ambient Hilbert space. This work sharpens and extends earlier results of G.~Glaeser on paratingents. As byproducts we obtain smoothing theorems for compact subsets of Hilbert space and disjunction theorems for locally compact subsets of Euclidean space.

Keywords:tangent space, diffeomorphism, manifold, spherically compact, paratingent, quasibundle, embedding
Categories:57R99, 58A20

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