Stefan Ram

2023-08-02 17:11:06 UTC

In the third lecture of the series "New Revolutions in

Particle Physics: Basic Concepts" (Fall, 2009) from "The

Theoretical Minimum", Professor Susskind talks about what

a quantum field is and how it is related to particles.

He considers a circle with a coordinate "x" and an amplitude

"exp( i k x )", and says that the momentum "p" is "hbar k".

Then he says (about 8 or 9 minutes into the video):

|"k" is called the "wave number". Uh. It's a wave number.

|And it can be positive or negative? Waves moving to the left,

|moving to the right, corresponding to momenta, going to the

|left or the right.

How can he talk about "waves moving to the left" if his

amplitude "exp( i k x )" does not depend on the time

(contains no "t")?

Do you think that "exp( i k x )" without "t" in his model

means that the amplitudes are constant (not depending on

the time) or is "exp( i k x )" a snapshot of the situation

taken at one instant (but actually depending on the time)?

Particle Physics: Basic Concepts" (Fall, 2009) from "The

Theoretical Minimum", Professor Susskind talks about what

a quantum field is and how it is related to particles.

He considers a circle with a coordinate "x" and an amplitude

"exp( i k x )", and says that the momentum "p" is "hbar k".

Then he says (about 8 or 9 minutes into the video):

|"k" is called the "wave number". Uh. It's a wave number.

|And it can be positive or negative? Waves moving to the left,

|moving to the right, corresponding to momenta, going to the

|left or the right.

How can he talk about "waves moving to the left" if his

amplitude "exp( i k x )" does not depend on the time

(contains no "t")?

Do you think that "exp( i k x )" without "t" in his model

means that the amplitudes are constant (not depending on

the time) or is "exp( i k x )" a snapshot of the situation

taken at one instant (but actually depending on the time)?