Quantum absolute 0

[Sorcerer]

From wiki:

A system at absolute zero still possesses quantum mechanical zero-point energy, the energy of its ground state at absolute zero. The kinetic energy of the ground state cannot be removed.

Is this ground state equal to the combined spins of the particles in the system. Is the kinetic energy only angular momentum?

Edited December 24, 2015 by Sorcerer

[Strange]

One (informal) way of understanding the zero point energy is through uncertainty. There is uncertainty in the energy of a particle, which you can think of as it having a distribution of energies around the expected value. Well if the expected value is zero, that distribution cannot go negative so there is small shift up from the expected zero value.

[timo]

Is this ground state equal to the combined spins of the particles in the system. Is the kinetic energy only angular momentum?

Not necessarily. The prime example for a quantum mechanical system with non-zero energy of the ground state (and zero energy ground state for the corresponding non-QM systen) is the harmonic oscillator. This energy is a mix of potential energy and kinetic energy. The kinetic part is usually not attributed to an angular momentum, certainly not to a spin.

[Strange]

BTW. This website has a great selection of articles introducing the ideas behind quantum theory: http://profmattstrassler.com/articles-and-posts/

[Mordred]

One of my favourite intro websites. Very informative read

[Sorcerer]

Spin = kinetic energy - right?

You can't have a particle without spin, even at 0 kelvin - right?

 

 

So even without 0 point energy, they would still have KE. Right?

 

I guess the wiki was only referring to heat energy.

[swansont]

Spin = kinetic energy - right?

You can't have a particle without spin, even at 0 kelvin - right?

 

 

So even without 0 point energy, they would still have KE. Right?

 

I guess the wiki was only referring to heat energy.

 

I don't recall any situations of spin being associated with KE.

 

Anyway, there are particles or systems with integer spin, so you could have zero spin. The example timo gave of the harmonic oscillator is derived with a spinless particle — that's not the source of the zero point energy.

[Sorcerer]

 

I don't recall any situations of spin being associated with KE.

 

 

I thought spin = angular momentum = kinetic energy. This is correct right?

 

 

 

Anyway, there are particles or systems with integer spin, so you could have zero spin. The example timo gave of the harmonic oscillator is derived with a spinless particle — that's not the source of the zero point energy.

 

 

By having spin = 0 do you mean in total spin of the individual particles, or total spin of the system? In a Helium atom, could you explain why we take total spin and not composite spins. Why then is the spin of a particle important, why not the system? If so, what makes composite spins important in a system of particles, but not important within a particle?

 

How do spins cancel, is it directional, ie 1/2 spin clockwise + 1/2 spin counter clockwise = 0? I can't think of any other way, since negative spin makes no sense.

 

Wiki lacks a simplified explanation, I began getting into magnetic moments and types of spin, it's there somewhere, but a simple sentence would help. I notice Higg's Bosons have 0 spin, are these the only elementary particle thought to? Does this mean spin isn't a required property of a particle?

[swansont]

Angular momentum is not KE. Momentum is not energy.

 

Spin is a vector, so negative spin is that with the spin axis in the opposite direction of positive spin. From a vector standpoint, negative spin should make perfect sense.