Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 148734

A Banach space is a complete normed vector space: A vector space equipped with a norm such that every Cauchy sequence converges.

4 votes
1 answer
136 views

Are unit balls in Banach spaces retracts of bidual balls?

Let $X$ be a separable Banach space embedded canonically in $X^{**}$. Is there a retraction from the unit ball $B_{X^{**}}$ of $X^{**}$ onto the unit ball $B_X$ of $X$? When we insist on uniformly co …
A. U.'s user avatar
  • 97
4 votes
1 answer
361 views

Approximation property of a Banach space in terms of finite-rank projections

Let $X$ be a separable Banach space. Is this property equivalent to the approximation property? There exists a chain $X_n$ of finite-dimensional subspaces of $X$, each being a range of some projectio …
A. U.'s user avatar
  • 97
1 vote
1 answer
192 views

Strictly increasing functions in reflexive subspaces of $C([0,1])$

By the Banach-Mazur theorem, every separable Banach space $X$ embeds into $C([0,1])$. When $X$ is reflexive, it is not possible to find a sequence of disjointly supported, non-negative functions in an …
A. U.'s user avatar
  • 97