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An acute look at underbar{basic} facts concerning underbar{unbounded} subnormal operators is taken here. These operators have the richest structure and are the most exciting among the whole family of beneficiaries of the normal ones. Therefore, the latter must necessarily be taken into account as the reference point for any exposition of subnormality. So as to make the presentation more appealing a kind of comparative survey of the bounded and unbounded case has been set forth. oindent This piece of writing serves rather as a practical guide to this largely impenetrable territory than an exhausting report.
It has been argued that certain broad absorption line quasars are viewed within 35 degrees of the axis of a relativistic radio jet, based on two-epoch radio flux density variability. It is true if the surface brightness of a radio source is observed
In open question answering (QA), the answer to a question is produced by retrieving and then analyzing documents that might contain answers to the question. Most open QA systems have considered only retrieving information from unstructured text. Here
We introduce a new dataset for Question Rewriting in Conversational Context (QReCC), which contains 14K conversations with 80K question-answer pairs. The task in QReCC is to find answers to conversational questions within a collection of 10M web page
Open-domain Question Answering (ODQA) has achieved significant results in terms of supervised learning manner. However, data annotation cannot also be irresistible for its huge demand in an open domain. Though unsupervised QA or unsupervised Machine
Let $A, B$ be $ntimes n$ positive semidefinite matrices. Bhatia and Kittaneh asked whether it is true $$ sqrt{sigma_j(AB)}le frac{1}{2} lambda_j(A+B), qquad j=1, ldots, n$$ where $sigma_j(cdot)$, $lambda_j(cdot)$, are the $j$-th largest singular valu