What does a lower case r mean over variables in an equation?

[cryforhelp104]

TL;DR

What does a lower case r mean over variables in an equation?

I've attached an example here.

 

[jedishrfu]

Can you provide some context like what book you found this notation or in what topic the equation is used?

 

[FactChecker]

I am not familiar with that as a common notation. The book or article should define that notation someplace before it is used. It is not uncommon for me to have to scan back through the text looking for a notation definition. If you are lucky, there might be a section where all notation is defined.

 

[cryforhelp104]

Can you provide some context like what book you found this notation or in what topic the equation is used?

Hi, I attached a photo above. I've re-attached it here

 

[cryforhelp104]

I am not familiar with that as a common notation. The book or article should define that notation someplace before it is used. It is not uncommon for me to have to scan back through the text looking for a notation definition. If you are lucky, there might be a section where all notation is defined.

Unfortunately, the notation is from a power point and has no references.

 

[jedishrfu]

When we ask for context, we mean some reference either a mathematical field like geometric calculus or a book where’s it’s used Or the problem in which it was used.

Did this come up in a discussion for a new battery technology? What does the script E stand for? Electromotive force? Is the R some sort of battery resistance?

Could this be some kind of directional derivative along a position vector R or does R represent the real number system?

There is no way to help you here without some context.

Your reluctance implies this is some sort of privileged information from either a company or government source and you can’t divulge that if so then there’s nothing more to do here.

I’ve searched several places and have come up with nothing of note so we are at a dead end without context.

Lastly, please don’t give out any corporate confidential or classified information here.

My suggestion is to go ask the PowerPoint presenter what it means.

 

[cryforhelp104]

When we ask for context, we mean some reference?

What does the script E stand for?

Could this be some kind of directional derivative along a position vector R or does R represent the real number system?

There is no way to help you here without some context.

Your reluctance implies this is some sort of privileged information from either a company or government source and you can’t divulge that if so then there’s nothing more to do here.

I’ve searched several places and have come up with nothing of note So we are at a dead end without context.

Lastly, please don’t give out any corporate confidential or classified information here.

My suggestion is to go ask the PowerPoint presenter what it means.

Dude... it's one of Maxwell's equations. This is from a publicly available slide in my modern physics lecture. The E script stands for the electric field. The powerpoint doesn't have references. The link to the publicly available powerpoint is here. It's on slide 25.

 

[jedishrfu]

They start to use the notation on slide 7 without any description.

from the F=ma equation it looks like it’s just saying the F is a vector function.

maybe they couldn’t place vector arrow notation on the vector quantities and so used an R instead.

 

[Mark44]

Dude... it's one of Maxwell's equations.

It would have been good to tell us this, dude.

TL;DR Summary: What does a lower case r mean over variables in an equation?

View attachment 338492
I've attached an example here.

The 'r' characters in the image are an artifact of copying from the PowerPoint deck. They are supposed to be arrows that signify vectors. The characters aren't present in the original deck.

Here's how the image originally appeared.

The same problem appears on slide 7 of the deck.

 

[jedishrfu]

@Mark44 Great sleuthing! How did you find the original text?

Looks like the beginnings of a bug report for better Powerpoint font mapping.

 

[Mark44]

Great sleuthing! How did you find the original text?

From the link that the OP showed.

The link to the publicly available powerpoint is here. It's on slide 25.

 

[Vanadium 50]

Dude...

Dude, lose the 'tude!

I downloaded the file in question, and guess what? The r's turned into little overhead vector arrows.

And had you posted this link in the OP rather than play the game "Tell the people on PF as little as possible and make them guess" you would have had your answer in an hour and not a day.

Dude.

 

[berkeman]

Thread paused pending Moderation...

(biting my lip)

 

[berkeman]

After a Mentor discussion, the thread will remain closed. Thanks for the great find to explain it, @Mark44