# Search results for query: *

1. ### Suggestions for sources with detailed calculations in quantum field theory.

I agree that an average student should be able to do the calculations but perhaps at initial stage he or she may need some assistance. (At least someone like me would need.) I would consider standard qft books at the level of Peskin and Schroeder.
2. ### Suggestions for sources with detailed calculations in quantum field theory.

Can you suggest any source available on internet which may be particularly helpful for those studying/brushing up knowledge of classical or quantum field theory without help of any teacher or friend? Some calculations are at first not so straightforward and there are many types of calculations...
3. ### Confused about method to approximate a decimal number.

Homework Statement I need to approximate the number 14.45 to nearest integer. Homework Equations The Attempt at a Solution If I remember correctly, to approximate a decimal up to say 2nd decimal place, I look at the third digit and if this is greater than or equal to 5, then I...
4. ### What value is expected for baryon to photon density?

It is generally stated that observed baryon to photon density (about 6.1x10^(-10)) is too small. What is the reason? What ratio is expected?
5. ### Is spending huge money on high energy physics expt justified?

I am asking this question here rather than in some other forum assuming most of those interested in HEP visit this forum. I personally believe that high energy physics attempts to find answers to some of the most fundamental questions in nature and hence spending huge amount of money for this...
6. ### A few doubts about quantum field theory and high energy physics.

It would be interesting to see if there is an example where a problem can be solved both perturbatively and non-perturbatively and to check if these give same results. Also in case of perturbative calc we should see upto what order the results are same. Perhaps for harmonic oscillator we can do...
7. ### One doubt about string theory.

Thanks for the responses. However I still do not understand why it should matter whether the parameter we are talking about is dimensionless or dimensionful.
8. ### One doubt about string theory.

I read somewhere that one power of string theory is that there is no adjustable dimensionless parameter in the theory. Why is this considered a strong point in favour of string theory? Second, how does the theory help in solving cosmological constant problem? Again there is no adjustable...
9. ### A few doubts about quantum field theory and high energy physics.

1. I read that the picture of gauge bosons as mediators of interaction originates in and is valid in perturbation theory. But how do we know that picture is correct? We do perturbation theory only because we do not know how to study a system in a fully non-perturbative way. If someday we...
10. ### LaTeX Are journal-specific latex packages compulsory for writing articles for them?

Many journals encourage authors to use their special latex packages (e.g., revtex4-1 for physical review a,b etc) while sending an article for peer-review process. I am not sure if this is compulsory or optional. Will an article be rejected if it is written not using the special latex packages...
11. ### How to calculate magnetic/electric field near an overhead power line?

The usual overhead power distribution wires are said to have potential of 230V in a certain locality. (These are voltage levels in wires seen along streets electricity pillars and these enter house of consumers.) How does one calculate magnetic field and electric field produced by the wire at a...
12. ### Principle of superposition for a particular case of liner differential equation.

Suppose a given second order linear differential equation has two different solutions; then it follows that their linear combination is also a solution. If y_1(x), y_2(x) are two solutions then y(x)=a_1y_1(x)+a_2y_2(x) is also a solution where a_1, a_2 are two constants. If we consider the...
13. ### Please suggest some material for quick review of general relativity.

There are several online materials on general relativity. Here I would like to get suggestions about concise review of general relativity at somewhat advanced level. The idea is that this should be enough for recapitulating the area at advanced level by somebody who had studied it thoroughly...
14. ### Calculation of concentration of a solution.

How does one take into account the fact that volume of a solution increases upon dissolving solute? which volume should be taken as the net volume, the volume of solvent to start with or the full volume of the solution? Suppose I add 20gm of sugar in 100cc (or ml) of water. After sugar...
15. ### Does the universe have an edge?

Does it make sense to say that the universe has an edge/boundary? Neutrinos are moving all the time with practically no interaction i.e., unimpeded. Where are these reaching after a very long time (t->infinity)?
16. ### Roots of SU(3): Basic Constructs & Generators

Thanks for the explanation. I'll check it and come back soon.
17. ### Roots of SU(3): Basic Constructs & Generators

I have some doubts regarding SU(3). These are at very basic level. First, how does one construct adjoint representation of SU(3)? What will be the dimensionality of the matrices? The defining matrices in terms of Gell-Mann matrices are 3x3 but in the case of adjoint representation the matrices...
18. ### What does this remark by Einstein mean?

What did he have in mind when he remarked: "Everything should be made as simple as possible, but not simpler."
19. ### What is meant by a certain theory has a scale ?

What is meant by "a certain theory has a scale"? In the context of high energy physics (and in other branches too) I sometimes hear that a certain theory has "an intrinsic scale in it (the theory)". What is implied by that? How do I find out if a given theory has a scale in it? Can there be...
20. ### Why global conservation of certain physical quantities is not enough?

What is the implication of the fact that quantities like electric charge, color etc are conserved not just globally but in local region of space too? I understand the later is more restrictive but what advantage does it offer?
21. ### Number of generators of SU(n) group

How do I calculate the number of generators of SU(n) group (which is extremely important in particle physics)? In the case of SO(n), I can do that using the physical interpretation of the group, i.e., it is related to rotations in n-dimensional Euclidean plane. What do I do in the case of SU(n)...
22. ### How do I calculate number of generators of SO(5)?

Thanks a lot for your reply. I understand this now.
23. ### References for Nonlinear Sigma Model.

Can anybody please suggest some references (preferably review articles or lecture notes etc, freely available online) for learning linear and nonlinear sigma models and their applications in particle physics?
24. ### How do I calculate number of generators of SO(5)?

The group SO(5) is relevant at times in particle physics. Can anybody please explain how to calculate the number of generators of SO(5)?
25. ### Question regarding research (related to research topic and writing thesis)

I have three questions: 1. Suppose your supervisor has given you freedom to choose topic of research (for PhD). How do you decide what topic to work on? 2. Can one work on two somewhat disconnected topics and write about both in same thesis? 3. When do you feel that you have done enough...
26. ### Research in high energy phenomenology.

Thanks for the response. Yes the answer does help. I am asking because I may join research in near future and I have option to work in the area I mentioned. I have learned some parts of the Peskin-Schroeder book but not 100% of it.
27. ### Research in high energy phenomenology.

For doing research in high energy physics phenomenology, specially in physics beyond standard model, what background should one have? What are the tools researchers in this area generally use? Do you think research in this area to be hard? In phenomenology papers, sometimes very complicated and...
28. ### What is the purpose of a seminar ?

What is the purpose of a "seminar"? In academic environments, seminars are so common. People speak in seminars and people listen to others talking in seminars. Can anybody please tell me why seminars are important? Why is it important for a speaker and for a listener? Why do people speak in a...
29. ### What is the difference between a parameter and a variable?

It seems (to me) that parameters are also kind of variables in descriptions of physics. I am confused what makes a paramater different from a variable. Can anybody please explain this?
30. ### Suggestions for a beginning researcher.

What advice will you give to someone who starts as a graduate student (theoretical works) but since supervisor is rarely available for consultation, have to take the responsibility of making progress alone. Frankly I am in such a situation and even though I work a lot, I find I am making very...
31. ### Is use of bibtex more time consuming than old fashioned way?

I am trying to learn application of bibtex. I do not understand why people claim that use of bibtex simplifies creation of bibliography in a latex document. In order to cite references from a bibliography database, I first need to create the required file (with .bib extension) and then call it...
32. ### Derivation of Thomas Precession formula

I am looking for a derivation of Thomas Precession formula in special relativity. can anybody please suggest any online source (or book) for this?
33. ### Momentum four vector for ground state.

I am confused about the definition of ground state and its characteristics. For a field in spacetime do we mean the ground state to be the minimum of the potential or minimum of the total energy? Specifically what is the momentum four vector of the ground state ( p^{\mu}=(...) ) for a massive...
34. ### Relevance of supersymmetric quantum mechanics?

It is known that supersymmetric quantum mechanics based methods offer (less laborious) solutions to many problems where conventional methods (of solving Schrödinger equation) are much more laborious. Apart from that, is there any other relevance of this subject? Does this provide any insight in...
35. ### Is it possible to balance research and family?

I find it tough to balance my research and my family and wonder how others succeed in this regard. Every serious researcher will agree, I hope, that research demands undivided attention for high quality work. How can then a researcher take care of her/his family adequately? Should she/he...
36. ### Which is the better way of doing theoretical research?

Thanks for the suggestions. I do agree with your views. My views are also changing: Now I think that the later approach is probably better suited for success in "research". Let's see if anybody else offers any other views or comments.
37. ### Which is the better way of doing theoretical research?

Thanks for the advice. Frankly speaking, I once started research, left it unfinished and joined a post of a teacher. But I always had research in mind and since I have some time to spend on it now, I am again trying to come back to research. Unfortunately I do not have a supervisor right now and...
38. ### Which is the better way of doing theoretical research?

I heard some supervisors ask their students to first learn the subject and then start working on a problem. Some other supervisors ask their students not to spend much time in reading but directly start working on a problem. Then it becomes the duty of the concerned student to learn what is...
39. ### What is/are the correct way(s) to learn Physics ?

Thanks for sharing your views. Personally I feel if I use knowledge of physics to satisfy my curiosity about how things happen in nature, it becomes enjoyable. Otherwise learning physics becomes like accumulating information, kind of a burden. Earlier when I was a student of lower class, I used...
40. ### What is/are the correct way(s) to learn Physics ?

What is/are the correct way(s) to learn "Physics"? I would like to see what opinions others have regarding this point. How can one learn and enjoy "Physics" at the same time? There may not be an answer applicable for all but still some common advices may be given. I wonder when can one...
41. ### What role does torsion'' play in string theory?

What role does "torsion'' play in string theory? In general relativity we assume that connection is torsion free. However from a purely geometrical viewpoint, the concept of torsion can not be ignored (theoretically) and in string theory, it is said that "torsion" does play its role. Can...
42. ### Supergravity for beginners.

Thanks for your responses. I have come across some review articles but I am not sure exactly which one would be best to learn from. Since I will have to learn myself, first I want to be sure about a particular source. In past I have at times felt this difficulty: I grabbed whatever source I...
43. ### Supergravity for beginners.

Can you suggest any lecture notes/review articles/free books available in the internet at introductory level and which uses standard conventions in use at present? Thanks.
44. ### What is meant by the term gauge singlet ?

What is meant by the term "gauge singlet"? Can anybody please explain what is meant by the term "gauge singlet"? To be more specific, I got the term in a discussion on wess-zumino lagrangian where the superpotential contains the term:a_i \phi_i . The author claims that in order the theory to...
45. ### What is meant by Renormalon ?

Thanks, genneth. Regarding your comment about my identity, I am trying to understand qft and intend to become a theoretical particle physicist. I will look it up from peskin and schroeder.
46. ### What is meant by Renormalon ?

What is meant by Renormalon"? Can anybody explain what is meant by Renormalon"? What is its significance?
47. ### Doubt about D0 brane.

As far as I know a D0 brane is same as a point particle. If that is true then its presence in string theory would go against the very philosophy on which string theory is based (due to presence of 0-dimensional objects). Is my understanding correct? Also it seems to me that D0-D0 brane...
48. ### Nature of quantum theory of gravity.

Can anybody explain why the theory describing quantum gravity is expected to be discrete (rather than a continuum theory), nonlocal (rather than a local theory) and Lorentz violating (rather that a Lorentz invariant theory)?
49. ### Why is gravitino a spin 3/2 particle?

Graviton is a spin 2 particle. Why is its superpartner gravitino a spin 3/2 (2-1/2) particle and not a spin 5/2 (2+1/2) particle?
50. ### Gravitons corresponding to flat spacetime.

Thanks, Haelfix. You gave an interesting answer but I am yet to understand a few points. Please clarify if you have time. First, though I have not tried to do any calculations, I guess from the last line of your answer, that gravitons corresponding to flat spacetime will be constants in time...