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Search options not deleted user 88133

This tag is used if a reference is needed in a paper or textbook on a specific result.

4 votes
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Question about properties of affine varieties defined by bihomogeneous polynomials

Since each $F_i(u_1,\dotsc,u_{n_1},v_1,\dotsc,v_{n_2})=0$, then $F_i(su_1,\dotsc,su_{n_1},tv_1,\dotsc,tv_{n_2}) = s^{d_1}t^{d_2} F_i(u_1,\dotsc,u_{n_1},v_1,\dotsc,v_{n_2})=s^{d_1}t^{d_2}0 = 0$. So ce …
Zach Teitler's user avatar
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3 votes
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"Classical" proof that maximal minors form a Grobner basis under diagonal term order

Here are a few articles that might be relevant: Narasimhan, The irreducibility of ladder determinantal varieties, from 1986. It takes about 20 pages to prove the result (that the minors are a standard …
Zach Teitler's user avatar
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4 votes
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Polynomial as a sum of powers of linear forms (with restrictions)

Yes, it is true. Every polynomial does have a decomposition like you ask for, with restrictions. To explain why this is the case, first suppose that $p$ is homogeneous of degree $d$, and we seek a dec …
Zach Teitler's user avatar
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5 votes

Reference request: A multidimensional generalization of the fundamental theorem of calculus

The $p=2$ dimensional case is an exercise in Rogawski's calculus textbook. It is exercise 47 on page 885, section 15.1 (Integration in Several Variables) in the 2008 Early Transcendentals edition.
Zach Teitler's user avatar
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6 votes
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Very general quartic hypersurface in $\mathbb{P}^3$ has Picard group $\mathbb{Z}$

That is the Noether-Lefschetz theorem. Searching online should find plenty of results in web pages and lecture notes. If you want a published source, how about: Mark Green, A new proof of the explicit …
Zach Teitler's user avatar
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1 vote
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Extending a continuous map over projective space

Your condition (1) means: if $\hat{u}$, $\hat{v}$, and $\hat{w}$ are linearly dependent, then so are $\widehat{\varphi(u)}$, $\widehat{\varphi(v)}$, and $\widehat{\varphi(w)}$. So $\varphi$ preserves …
Zach Teitler's user avatar
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2 votes
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Secant variety to a zero-dimensional projective variety

I believe this would be a dual arrangement of a star arrangement. A star arrangement is a union of subspaces defined as follows. Let $H_1,\dotsc,H_d$ be a collection of hyperplanes and fix an integer …
Zach Teitler's user avatar
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65 votes

Why is the Vandermonde determinant harmonic?

Consider the symmetric group action permuting the variables. The Vandermonde determinant $V$ is antisymmetric, meaning it spans an alternating representation—it's invariant under permutations, up to m …
Zach Teitler's user avatar
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2 votes

Online events during the quarantine

AMS has started a list, organized by mathematical field, at https://www.ams.org/profession/online-talks.
2 votes

Reference on the classification of (low rank) Gorenstein rings over $\mathbb{C}$

This paper might possibly be relevant: http://www.ams.org/mathscinet-getitem?mr=2922602 It's not quite exactly what you are asking for. Instead of Gorenstein algebras of low rank, they are consideri …
Zach Teitler's user avatar
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3 votes
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Schubert varieties and Young diagrams

All values of $(i,\lambda_i)$ appear. The ones that aren't outside corners are redundant.
Zach Teitler's user avatar
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32 votes
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Is every real number in [0,1] a product of three (or more) Cantor set's numbers?

Yes, every real number $u \in [0,1]$ can be written as $u = x^2 y$ where $x,y \in C$ are in the Cantor set $C$. In particular, every real number in $[0,1]$ is a product of three Cantor set elements. T …
Zach Teitler's user avatar
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14 votes

What are examples of books which teach the practice of mathematics?

Two books by David Bressoud: Bressoud, David M. Proofs and Confirmations. The story of the alternating sign matrix conjecture. MAA Spectrum. 1999 "My intention in this book is not just to descr …