Recent content by Matt Smith

I was recently accepted into two master's programs. One is the two-year track Theoretical Physics in The Master's programme Physics and Astronomy, a joint degree with Universiteit of Amsterdam. The other is the Master of Science Programme (MSc) in Physics track "quantum Physics" of the...

I just want to know when we solve differential equation ,why choosing a different original point and axes won't make any difference.Curl and divergence rely on the x,y,z.So please ingore the relativity chapter in Jackson's book or griffiths,and take chapter3,or 4 as an example.In the first...

Ignoring special relativity theory，maxwell equation are deduced in which coordinate system?In most electrodynamics textbook,maxwell equation are deduced without specifying which coordinate we are using.For example,when we are solving poisson equation in static case，it seems we can freely choose...

It must be David Tong's lecture ,obviously.He is a professor in Combridge,and a nice guy.He put many of his lecture notes online in his website,very helpful.

Thank you.If we accept 100cm=1m,we can get a set which include all length.So maybe I can define for any x and y belong to the set,x+y=the total length.I could accept it in this way.I just think your definition is not so straightfoward

It is a great idea,honestly speaking.Like what happened in quantum mechanics,we use spin angular momentum and magnetic moment to describe a electron,even it can't really spin and it don't have a real magnetic moment(a generalized one percisely).But ,anyway,I won't study physics anymore,maybe I...

You are right.But I was so tired of physics recently,because why can't it be like math which just need proving.And F=Ma is neither a relation nor a definition.I get enough with it and I will go to study math.

As Feynman said,Newton's law is not well defined.In fact,we don't really know what it is,but we define it by F=Ma.It is not a relation but a definition.I don't really care about it because it can be applied very well ,or I can say, it do works!I prefer quantum mechanics and Lagrangian...

It is simple.Because work W=∑Fi*(the corresponding virtual dispalcement).Fi is generalized force.If W=0 under a virtual displacement,it means the total force is 0.Very simple.And if Fi is conserved force,V=-W.If W=0,potential energy don't change,but it is a function of the position.What is the...

We always define "+"by set theory.But in physics,it vanished,dispeared.In fact I think I should go to the math department when I am searching a master degree.

I just can't accept any addition principle. I don't know what had happened to me.I am very sure about what you have said before I learn linear algebra and abstract algebra.But now,it is difficult to take this problem as a pure physics problem.But if we ignore the math problem,how can we use...

No no no.Your explanation almost make me think I understand it.But in fact ,not.You can't say 10 y + 1 x = 0.1 x + 1 before you define the +.For example,we all know 2=2/1.But you can't say 2+7/8=2/1+7/8 before you define the +between rational number.Although in the history of math,we have to...

It seems reasonable to think like that.But it is too intuitive.There are many points to be not so strict.For example,why numbers with different unit can not be added.My question is ,is there any mathematical language which can define the addition and mulplication percisely?For example,"if we...

Not a bad choice.

I am an student in physics department and I will graduate very soon.In my past four year I have done a good work and get a nice gpa.But as I get more and more familiar with advanced content such as quantum field theory,I become very comfusing about what I learn in my high school. Because I...