# What symbol is this?

1. Mar 25, 2014

### Gabriel Maia

Hi. I was reading a chapter about Stationary Phase Method and I got stuck with this symbol $\Subset$. I looked it up on tables os mathematical symbols but could not find its meaning.

Can you help me?

Thank you.

2. Mar 25, 2014

### danjordan

I was reading about that from here http://www.math.ku.dk/~gimperlein/dif11/dif11_kim_stationaryphase.pdf [Broken] but saw no such symbol. What's your source?

Last edited by a moderator: May 6, 2017
3. Mar 25, 2014

### Gabriel Maia

http://www.math.purdue.edu/~sfholman/dHHU_Chap2.pdf [Broken]

First page, definition 2.1

Last edited by a moderator: May 6, 2017
4. Mar 25, 2014

### Hypersphere

This seems more like a math question to me (I've only seen it in functional analysis), but anyway. In this (and most cases), $\Subset$ tends to be used as an alternative to (the in my opinion rather ugly) $\subset\subset$, and means that one set is compactly contained (or embedded) in the other. For many intents and purposes, you can mentally replace $\Subset$ by the usual subset symbols ($\subset$ or $\subseteq$).