@JohnRennie, thanks, but the email should come in a few minutes (it said, probably going to actually be 6-8 weeks) and I'd rather have it under my own account.
@koolman if there isn't a lowest energy state for a system that means the energy can keep decreasing forever, and as the energy of the system keeps decreasing it can keep transferring energy to something else. So we have an infinite source of energy.
Since there are no infinite sources of energy (as far as we know) that means everything must have a lowest energy state.
@koolman a system can only fall into its lowest energy state if it can transfer its energy somewhere else.
For example an excited hydrogen atom can fall into the ground state if it emits energy as a photon.
That's why my example of a system with no lowest state works as an infinite energy source. It would be like a hydrogen atom continually emitting photons as it fell into lower and lower energy states.
@koolman it depends on the temperature of the system relative to its surroundings.
it's certainly true that if you put a system in a very hot environment then there will be a net flow on energy into that system, and the system won't be able to fall into its ground state.
So for example if we put a hydrogen atom into the Sun then it can't fall into the ground state because the Sun is so hot it heats up the hydrogen atom and keeps it excited.
I got stuck with some derivative, I can't think of a solutions for this, this is the last expression, because I am taking the derivative of a function with respect to it's integral basically?!?
I am looking to find some kinetic energy derivatives for lagrangian.
Help will be much apprciated.
@koolman Suppose you put a pendulum into a car and drive over bumpy ground. The ground state of the pendulum is to be hanging down motionless, but the car will keep the pendulum bob bouncing around so it can't settle into its ground state.
Imagine an infinite universe completely filled with pure, liquid water. Would there be any local pressure?
I think there should be, since the moving particles would hit any imaginary surface continually.
But how could this pressure be calculated?
The answer is that a static universe with the density of water would be closed not infinite and could be static only at the moment where it changed from expansion to recollapse.
@heather nitpick: It's helpful to break lines at the end of sentences in TeX. This makes looking at version control diffs a little easier. Not a big deal, just a tip.
But of course some Star Wars nerds not a million miles from here immediately objected that the joke should be What do you get if cross a vampire with an astromech droid?.
That may have confused you as we do not capitalize each word in titles on PSE. For works of literature/film/etc. one should capitalize each word (except for "of", "the", etc.).
@ACuriousMind Yes, it is ridiculous notation. I always write $\cos(x)^2$ in defiance of the stupidity.
@heather when you make a commit, if you put "Fixes #123" in the commit message, then issue #123 gets automatically closed when the commit is pushed to your master branch.
I'm not suggesting you should actually accept my request as it's a trivial change anyway, but this is how we nerds manage our multimillion line apps with multiple developers.
@Slereah 1. Nothing to do with QFT, it's a general thing that unbounded operators are only well-defined on a subset of $H$. 2. The exponential of such an unbounded operator will act on the closure of the domain of definition. If the domain is not dense, you can't act on all states with the exponential.
@koolman I think a larger dollop tends to flatten more, because the ratio of the surface to the volume is smaller.
I had a casual argument with some poeple about this spoon. I said I think it's about the size of a tablespoon, because of the shape of the cream (supposing it's actually cream).
@heather Since opening an issue just for a positive comment seems silly, let me say here that I'm overall impressed by the clarity of your writing. I didn't have to read a single sentence more than once to get what you mean, which is rare even in texts where I know the subject matter by heart.
Particularly the parting angle on the left side of the cream where it parts from the wood. It's too wide for a big amount of cream. Even whipped cream.
@ACuriousMind, thanks a lot! I'm glad its clear. Some of my friends asked me to type up some notes/problems for them, and this was going to be my response.
• The electronic configurations of Mn2+ is ([Ar]3d5) while for Mn3+ it is ([Ar]3d4). Assuming that in both compounds these ions are surrounded by an octahedral field of ligands, establish which one of the two ion is expected to have a larger anisotropy D.
@Slereah That's the general fault of much mathematical writing: They're so focused on being axiomatic and rigorous that they often forget to tell you why you should care about a particular definition.
I suspect it's because they often consider it obvious :P
In particular there seems to be a set of things that "everyone knows" in various experimental fields that are not obvious and are not widely known by people who haven't been involved in that kind of experiment.
SO we write just a few words in the paper because "everyone knows" and anyone from out side the clique find themselves at a loss.
My son watched one of the "Duct tape specials" of Mythbusters last night (his first time really watching the series). In the episode, they were marooned on an island and needed to, among other things, start a fire using duct tape.
This afternoon, I caught him trying to start a fire using sticks that he saw them use
@dmckee Well...that doesn't fit with your Oct '13 meta post talking about technology, though
Maybe I'm accessing the tag history wrong, or maybe the tag was briefly deleted and you re-created it
It's funny that in your post you seem to be sure what "technique" is about but not what's up with "technology", while I found myself in the opposite situation ;)
@ACuriousMind I'm not sure I ever made my clear on that and few other people use the technique tag. So if we are thinking ofkilling on that is something to consider.
@DanielSank Send the kid to live in the vents, terrorizing the family until they move out of the "haunted" house, then buy the cheap (because it's haunted!) house+ nice lawn for yourself.
I got stuck with some derivative, I can't think of a solutions for this, this is the last expression, because I am taking the derivative of a function with respect to it's integral basically?!?
I am looking to find some kinetic energy derivatives for lagrangian.
Help will be much apprciated.
Imagine an infinite universe completely filled with pure, liquid water. Would there be any local pressure?
I think there should be, since the moving particles would hit any imaginary surface continually.
But how could this pressure be calculated?
• The electronic configurations of Mn2+ is ([Ar]3d5) while for Mn3+ it is ([Ar]3d4). Assuming that in both compounds these ions are surrounded by an octahedral field of ligands, establish which one of the two ion is expected to have a larger anisotropy D.
