One can consider the Calabi-Yau threefold K3$\times E$ where the Donaldson-Thomas theory is conjectured to be the (inverse of) the Igusa cusp form $\chi_{10}(q,y,p)$. The variables $q,y,p$ aren't conventional, I just want to emphasize that it is a three-variable automorphic form. So we have
$$...
Why the electrostatic energy of a sphere of radius $a$ is less than the electrostatic energy generated by two particles at a distance equal to $a$?
I don't see it intuitively
The electrostatic energy of a sphere is $\dfrac{3}{5}\dfrac{Q^2}{4\pi\epsilon_a a}$ while the electrostatic energy of two particles at a distance is $\dfrac{Q^2}{4\pi\epsilon_a a}$
Just found a start-up that allows you buy fruits and vegetables online! They guarantee the quality of the fruits with the best price, and deliver in less than 2 hours.
@Sid I've heard of a startup in China that when you get stuck in traffic, they send 2 guys to you (using a motorcycle), one of them gets you to your destination using the bike and the other brings you your car :)
The system offers you all names that start with a non-letter/non-digit unicode character as autocomplete after typing the @ alone because on a standard keyboard it is hard for the ordinary user to produce these characters.
@Sid They've claimed they want to lower the prices by buying the fruits directly from the farmers and delivering to the consumer, and avoid all the unnecessary brokers in between....
@ACuriousMind OK, changed for now, until I come up with a name that actually works
@ACuriousMind I don't know if you remember me but a few months ago you helped me with a physics problem right before my exams. You seriously helped me think differently about alot of topics and helped me immensely for the rest of my exams. I'm extremely thankful for your help and I'd just like to tell you that I was able to score an A* in my physics exam
If centrifugal force doesn't exist, why do we feel it? For example while the car takes a turn we feel as though we are pulled away and not towards the centre of the circular path.
@Abcd I think it's sort of a word game: How do you define "centrifugal force" if not as the outward force felt by something in a rotating frame of reference?
@ACuriousMind We don't use the word "felt" in our definitions. But still, I don't get it. How can a false=non existent=pseudo force be felt by our body when in reality some other centripetal force is acting on us?
@Abcd Well, the point is that it's not "in reality" that the centrifugal force doesn't exist, it's in non-inertial frames that it doesn't exist. It exists, in every meaningful sense of the word, in rotating frames of reference.
@dmckee You are mixing the constant field and constant characteristics of the particle in the field. THEY are changing. And even for that, describing differential changes, the characteristics in the small area and time are viewed as constant. You simply do not understand differential maths. — Gangnus46 secs ago
