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    What is the meaning of a basis?

    Hi! There is a concept I don't understand and would love to have is cleared... What is the meaning of a lattice with a basis? What do I need it for? Say I have a honeycomb structure. (fig 1) and a basis as mentioned there (did I understand it right? is it the basis? ) why does it become...
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    Transistor circut analysis

    Thank you both for your great help!
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    Transistor circut analysis

    Hi there! I'm having trouble understanding the transistor circuit analysis. Hope you could help me :) First I need to find the active region of the transistor. What I saw in the solutions was an assumption that the transistor is in saturation region and then: VBB=IbRb+Vbe+IeRe...
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    Mathematica Mathematica help

    Hi! I hope this is the right forum... I am having trouble with Mathematica: Maybe someone could help out of his experience ? I created w[x]:=RandomReal[NormalDistribution[0,1],x] I got it's plot. Now I want to integrate it: I wish to receive another graph, which is the plot of the...
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    Notation problem

    I will take advantage of your kindness and ask another thing: For m^2<0: W^\mu=\frac {1} {2} \varepsilon^{\alpha\beta\gamma\delta}M_{\beta\alpha} p out of it we will get both L's and K's, meaning the algebra is not close in su2. so, there is no finite way to write the states you can get...
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    Notation problem

    Thank you so much for a wonderful reply!
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    Notation problem

    I don't know... an adjoint term maybe?
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    Notation problem

    Hi! I can't understand something in field theory and need your assistance: I wish to understand why a particle of mass m^2<0 can't exist. For a massive particle, in its reference frame, one would write: p_\mu=(m,0,0,0). I understand that. But for m=0, why is: p_\mu=(p,0,0,p) And for m^2<0...
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    Understanding definitions

    Thank you! But why does p_{\mu}=(0,0,0,m) relate to m^2<0? And likewise, p_{\mu}=(p,0,0,p) relate to m=0? I understand why p_{\mu}=(m,0,0,0) relate to massive particle, My logic here is p_0=E and E\approx m and \vec{p}=0 (because we are looking at the reference frame) But...
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    Understanding definitions

    Hi guys! There is something I would like to get your help with... I am looking at the equation: W^{\mu}=-\frac{1}{2} \varepsilon^{\mu\nu\lambda\sigma}M_{\nu\lambda}p_{\sigma} Which is, if I understand correctly,a Casimir Operator. Now, I wish to look at a particle in its rest reference...
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    Commutators, etc.

    I will never get used to this type of writing.... and to think it was invented to make things simpler... I'd rather just write the whole thing. I am sorry but there is something I fail to understand. What are the relations between M_{\alpha\beta} and M^{\alpha\beta}? Why can't I switch the...
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    Commutators, etc.

    Oh... then there's a problem here... what do I do when I am given M_{\alpha\beta} and what I need is M^{\alpha\beta}? I have an exercise in which I have to prove that : [M^{\alpha\beta},P^{\gamma}]=0 and I need to use M_{\alpha\beta}
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    Commutators, etc.

    Is it correct to write: M_{\beta\alpha}=g_{\alpha\alpha}g_{\beta\beta}M^{\alpha\beta}
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    Commutators, etc.

    Wow... thank you so much for this wonderful reply...I am still trying to understand the whole thing... :)
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    Commutators, etc.

    Hi you guys! I am having a hard time understanding some stuff in this context. I was not able to find any guidance in books or anything. say I want to calculate: [W^2,p^\alpha]=0, W=\frac{m}{2}\varepsilon^{\mu\nu\lambda\varepsilon}M_{\mu\lambda}p_\delta How do I do that? I can't...
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    Why change the coordinates?

    Hello! I have a question regarding a method I saw every now and then: Say I have a system containing of two masses, attached to one another by a spring. Each is attached to a wall by another spring. Now I wish to know the eigen vectors and eigen values( \omega) of movement. I get: \ddot...
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    How to find primitive function?

    Hello! I am having trouble understanding the whole primitive function thing in complex analysis. How do I check if a certain function, say [itex] \frac {sin(z)} {z} [/tex] has a primitive, say in C/{0} ? What is the intuition? My intuition is that 0 is the only singularity, so if it is...
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    Finding Geodesics What I wish to understand, is how to solve

    Hi... I did not understand what you meant. I integrate with respect to lambda... not d/d(lambda) ... Thank you
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    General question about E-L in revativity

    Hello! I ask this question in this forum because I wish to be given a general explanation. Hope it is OK given this metric: ds^2= \frac {dt^2} {t^2}- \frac{dx^2} {t^2} I wish to calculate the geodesics. S=\int{ \frac {d} {d\lambda} \sqrt{\frac {1} {t^2} \frac {dt^2} {d\lambda^2}-...
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    Finding Geodesics What I wish to understand, is how to solve

    Finding Geodesics What I wish to understand, is how to solve this one: given this metric: ds^2= \frac {dt^2} {t^2}- \frac{dx^2} {t^2} I have to calculate the geodesics. S=\int{ \frac {d} {d\lambda} \sqrt{\frac {1} {t^2} \frac {dt^2} {d\lambda^2}- \frac{1} {t^2} \frac {dx^2}...
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    Another gravitation problem

    Anybody...? I am lost in here ... Thanks
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    Another gravitation problem

    Hello! I need to find the relation between E^{2}-B^{2} and F_{\mu\nu} F^{\mu\nu} Actually, I need to use this relation to determine that the first is a scalar. What I can't understand is how these notations match the formal definition: If I multiply a matrix by another (same size) I should...
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    Gravitation question

    Got it- Thanks to you! Thank you so much!
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    Gravitation question

    Thank you so much for your reply... Yap, all the typos you found are typos... Actually, I did what you wrote (well, most of it) before, and still can't solve... But you did clear some things for me, and thank you for that... I know how the F tensor looks like (I just have no idea how to...
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    Gravitation question

    Hello! I fail to understand this question... I don't even know how to approach it... Given: m\frac{d^{2}x^{\mu}} {d\tau^{2}} =e{F^{\mu}_{nu}} \frac{dx^{\nu}} {d\tau} I have to define u^{\mu}= \frac {dx^{\mu}} {d\tau^2} and obtain: u^0= cosh(\frac {eE\tau} {m}) u^0(0)+ sinh(\frac {eE\tau}...
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    Angular Mumentum: Question for my exam tomorrow

    Yes... that was the question... and I understood it, with your help... Thank you again!
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    Angular Mumentum: Question for my exam tomorrow

    mathfeel- I know these things. I just didn't understand why it is wrong to use just L^2. Thank you.
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    Angular Mumentum: Question for my exam tomorrow

    Yeah, my exam is tomorrow... The problem is, I am having a really hard time struggling with the English language's logic... My logic is taken from another language... Hebrew. despite the fact I understand every word alone- it is very hard to understand the whole thing. That is why, I guess...
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