Post by: paul cotter on 23/12/2022 16:01:14
Post by: Zer0 on 19/01/2023 17:37:54
(Current Professor or long retired)
Are We referring to a considerably Old Senior Citizen?
Post by: paul cotter on 27/02/2023 11:40:18
Post by: Bored chemist on 27/02/2023 18:19:34
Sometimes they turn out to be right. :-)
Post by: Eternal Student on 28/02/2023 02:59:16
He then states that the term grad div E represents the "scalar wave"Grad (of a thing) is always a vector not a scalar. So on the face of it I would be concerned about it being called the "scalar wave" - but I haven't looked at exactly what this professor did.
PS I apologise for alternating between the del operator and grad, div as I cannot get consistent use of symbols on this computer/operating system.Obviously what you have done is OK anyway. However, if you ever really wanted some mathematical notation then it can be done on any computer with any keyboard (e.g. a mobile phone) if you use LaTeX coding. I'll put all of this under a pull-down spoiler, since it's not essential for the original post or reply.
Spoiler: show
. Vectors as underlined characters 
looks neater than using a letter 
for multiplication or vector cross products.
but I prefer underlined vectors 
Back to your original post:
The identity
will hold for any sensible vector E.See half-way down the page here: https://en.wikipedia.org/wiki/Vector_calculus_identities#Second_derivative_identities
By sensible vector, I mean it's smooth enough - all the derivatives you would want actually do exist. You could have deliberately chosen a vector that had some discontinuity in some first derivatives if you wanted to invalidate that identity.
Note also that the operator ∇2 on the right hand side is understood to be the vector Laplacian (it acts on a vector to produce another vector). Assuming E is the electric field and satisfies Maxwell's equations then you automatically have most of what you'll need to be confident the vector function is smooth enough for that identity to hold. I haven't spent too long looking at it but it seems you would have to be deliberately trying hard to find a most unusual E field if you wanted to defeat that vector identity - so we'll just go along with the assumption the vector identity will hold.
So nothing much is wrong with what that professor said to this point. The only bit, as I said previously, that concerns me is the terminology "scalar wave". That's not terminology I'm familiar with and the thing isn't a scalar, it would be a vector.
Just from Maxwell's equations, we have Grad(E) = 0 in free space without any charges exactly as you stated, so yes all of what he/she is calling the "scalar wave" would become a 0 vector there. I'm going to assume the professor knows that and their "scalar wave" idea is only interesting in regions where there are charges. Overall impression ---> I wouldn't be rushing off to find out what the professor was trying to say (or sell) based on what you have written.
As regards the fuel thing. "An ice" can have a meaning other than the usual solid water ice. Here's an example:
In astrophysics and planetary science the term "ices" refers to volatile chemical compounds with freezing points above about 100 K, such as water, ammonia, or methane, with freezing points of 273 K (0°C), 195 K (−78°C), and 91 K (−182°C), respectively (see Volatiles). [Extract from Wikipedia: https://en.wikipedia.org/wiki/Ice_giant ]
Without reading the full details, maybe their ice thing could work.
Best Wishes.
Post by: paul cotter on 28/02/2023 12:37:57
Post by: Zer0 on 02/03/2023 22:44:43
Academia has to tolerate people who make absurd errors.
Sometimes they turn out to be right. :-)
You got any fun or entertaining Evidences?
Post by: paul cotter on 04/03/2023 10:59:12
Post by: Zer0 on 04/03/2023 20:46:47
Should people suffering thru Brain Fog be held accountable for what they say & do?
I'm observing something similar with Senior Citizens lately, they say absurd stuff n act crazy.
But undecided on whether i should view Them as Culprits or Victims?