Ahmed Sani

3 Questions 8 Answers 0 Followers

Questions related from Ahmed Sani

Is it possible to assign a given curve of monofunction on [0;1] to be a support of a copula (or copulas)?

Nelsen, in his famous book "Introduction to copulas", gave via examples (see paragraph 3.2.1) a way to construct copulas with prescibed support. He treated the case of segments and arcs of...

29 June 2020 1,995 0 View

What is the relation between general operator spectrum (no resriction on space nor on domain) and possibility for this operator to have square root?

It is known that for special cases, mainly for analytic position operators, the splitting of spectrum on two connected components ensures existence of square root (result of Gunter and Shaffer)....

17 December 2019 5,516 0 View

Is there an example of two closed subspaces E and F for which the sum E+F is not closed. Precision: E and f are subspaces of a Banach space X?

In finite dimensionnal spaces, the sum is evidentely closed. If one of the subspaces is of finite dimension, the result is a simple translation of closed subspace. The situation in infinite...

16 May 2018 8,506 9 View