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    How to interpret the field function Φ in QFT?

    Hi, I have a question that how to interpret the field function Φ in Quantum Field Theory. As I can see, it is an operator through second quantization and the co-ordinate representation no long exist after second quantization. So we cannot regard it as wave function any more. Could...
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    What would be the pre-requisites to learn Topological Quantum Field Theory?

    Personally, I am interested in Topological Quantum Field Theory. And now I am battling against Quantum Field Theory. I am not sure how much Quantum Field Theory is needed to do Topological Quantum Field Theory. And I am not sure what should be the mathematical pre-requisites of Topological...
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    What is internal space/internal symmetry?

    Hi, I have already been familiar with that exterior symmetry is the spacetime symmetry. Such kind of symmetry has been depicted by Poincare' group. Then I am still find the concept internal space/internal symmetry ambiguous. And I cannot understand why put Spin in exterior symmetry not...
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    What is Little Group ?

    What is "Little Group"? In my Quantum Field Theory class, I too often meet with the term "Little Group". Unfortunately, I cannot find a good description of Little Group until now. I just know it is a subgroup of Lorentz Group. Can anyone have any brief description of this concept? Or any...
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    Is there any good reference on Riemann Surface and Riemann Theta Function?

    Hi, Currently, I need to read some reference about Integrable System, but I am stuck in Riemann Surface, genus, divisors, and Riemann Theta Functions. This makes me anxious. Is there introduction or pedagogical reference on this topic? I think I can spend some time read it during winter...
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    What is the Genus of Riemann Surface?

    I learnt something about genus in Topology. The concept Genus in Topology is intuitive and lucid. Now I am confronted with the Genus in Riemann Surface. I do not know what is Genus on Riemann Surface. Is it relevant to "singularity"? Anyone can help me make it a bit clear? Thanks.
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    I made a mistake on Professor's Name, what should I do?

    I sent an E-mail to my professor Kaufmann, but I made a mistake on his name. I typed Kaufman, not Kaufmann. What should I do?
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    How can I access to the following reference?

    V. A. Belinskii and V. E. Zakharov, Integration of the Einstein Equations by the Inverse Scattering Method and Calculation of Exact Soliton Solutions, Sov. Phys. JETP 48, 985 (1978) I cannot access to in via the library in my department. But I need it in my research. Sad... The website...
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    Are there any book can serve as the companion book to Peskin's QFT?

    Hi, guys. I will start learning Peskin's QFT from the coming fall semester. I plan to spend 2 years for studying in order to strike a thorough understanding of QFT. Peskin's QFT book in general is a good one, but it focus on calculation techniques; thus, I think I need a companion book which...
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    Is it easy for international students in U.S. find job in college or in university?

    I am an international graduate student studying in U.S.. I am pretty not sure whether or not it is easy to find job in American university/college (gaining a teaching position) after graduation. I come from China, P.R., and now a physics graduate student in U.S.. I still have many years left...
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    If already known the Action and unkown the Metric, how to get geodesic equation?

    If already known the form of Action and unkown the Metric, how to derive the geodesic equation?
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    What is Expanding Horizon of a black hole?

    What is Expanding Horizon of a black hole? Recently, I want to read something general on Expanding Horizon...
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    A Question about Non Linear Differential Equation

    Given a non linear differential equation, we have know the symmetry of its solution. How can we finally get the exact solution? Any methods or reference? (I am a physics students; recently I met with something relevent to non linear differential equation.)
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    I want to buy two Quantum Mechanics books, what would be the best combination ?

    Hi, I want to buy two Quantum Mechanics books, but I am pondering what would be the best combination. My definition of BEST is resourceful, lucid, in-detail. As a physics student, I think two quantum mechanics books putting on my shelf is quite enough... My List: David Bohm, Quantum...
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    How can I write an Email to Professor?

    Recently, I am reading a paper from Ezra T Newman (in Pittsburg); I want to Email him to ask him a question about his paper. Unfortunately, I am an undergraduate have no such experiences. How should I write? Is there any templete?
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    How is Weyl Tensor associated with tidal force ?

    How is Weyl Tensor associated with tidal force? I checked my book, the acceleration in tidal effect can be expressed as: ac=-RabdcZawbZd Note: Za is the tangent of geodesics, wb is the seperation vector I cannot see from this equation how Weyl Tensor affects tidal force. It is...
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    Can I express stationary spacetime and static spacetime in this way?

    Can I express "stationary spacetime" and "static spacetime" in this way? Can I express "stationary spacetime" and "static spacetime" in this way? stationary spacetime: if we arrange a set of observers locating in any places, then each of them should observe nothing change at the place where...
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    How can this indicate rotation?

    If we say r2= (x-a)2 + (y-b)2 + (z-c)2 can generally represent displacement, why can r2= (x- ia)2 + (y- ib)2 + (z- ic)2 generally represent rotation? (i2 = -1) And why r2= x2 + y2 + (z - ia)2 represents rotation with respect to z axis
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    Can this represent rotation? Why?

    If we say r2= (x-a)2 + (y-b)2 + (z-c)2 can generally represent displacement, why can r2= (x- ia)2 + (y- ib)2 + (z- ic)2 generally represent rotation? (i2 = -1) And why r2= x2 + y2 + (z - ia)2 represents rotation with respect to z axis
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    How to denote tetrad in Abstract Index Notation ?

    I like Penrose's Abstract Index Notation very much. I am familiar with using Abstract Index Notation to denote Coordinate Basis. But when I try to denote tetrad with Abstract Index Notation, I meet problems. How to denote tetrad in Abstract Index Notation?
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    A problem in cyclic group

    Given a cyclic group of order n, with all its elements in the form : A, A2, A3, ..., An where A is an arbitrary element of the group. According to the definition of group, "The product of two arbitrary elements A and B of the group must be an element C of the group", That is...
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    Are Lx, Ly, Lz (the components of Angular Momentum)independent to each other?

    In Classical Mechanics, are the three components of Angular Momentum L: Lx, Ly, Lz independent to each other? It seems that there is an identity in Classical Mechanics (Sorry, I can hardly remember where I saw it): [Li, Lj] = εijk Lk. Note: [] is Poisson Bracket, εijk is...
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    Where can I find Survey of gravitational radiation theory F.A.E PIRANI

    Where can I find "Survey of gravitational radiation theory" F.A.E PIRANI Where can I find Survey of gravitational radiation theory F.A.E PIRANI I cannot find it in the library in my Univ. AND it is not available on google book. Desperate
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    How is Greenwood's Classical Dynamics?

    My friend recommend this book to me. Actually, I don't have enough time to read Goldstein. But this is book is not so thicker as Goldstein's. May I use this book as a substitution?
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    Is there any good reference of tetrad in GR

    I want to find a good reference in GR about the application of tetrad. Is there any good suggestions?
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    Any good references of Petrov Classification?

    Is there any good references of Petrov Classification? Thank you.
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    How to obtain Kerr Metric via Spinors (N-P Formalism)

    How to obtain Kerr Metric via Spinors (Newman-Penrose Formalism)? I am a bit confused with Ray d'Inverno's Book. Why perform the coordinates transformation: 2r-1 -> r-1 + r*-1 I am bit confused of it. And I am a bit confused, too, of how to write out null tetrad...
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    Advanced/Retarded Eddington-Finkelstein Coordinates and Incident/Outgoing Wave

    My professor said that Advanced Eddington-Finkelstein Coordinates CAN be applied to describe incident wave well, while CANNOT describe outgoing wave. Conversely, Retarded Eddington-Finkelstein Coordinates CAN be applied to descibe outgoing wave well, while CANNOT describe incident wave...
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    What is Newman Penrose Formalism?

    What is Newman Penrose Formalism? Are there any easy-to-read references? I find their original work on N-P Formalism, but only find it is a bit difficult for me... Thank you.
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    How to calculate the contraction of metric tensor g^ab g_ab

    I wish I could calculate the contraction: gabgab I wish someone could show me how to get n! Unfortunately, I find it difficult, for I am not familiar with Tensor Algebra ... My wrong way to calculate it: gabgab= gabgba (since gab is symmetric) = δaa = 1 Why is it wrong?
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