What is Theoretical physics: Definition and 543 Discussions

Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experimental tools to probe these phenomena.
The advancement of science generally depends on the interplay between experimental studies and theory. In some cases, theoretical physics adheres to standards of mathematical rigour while giving little weight to experiments and observations. For example, while developing special relativity, Albert Einstein was concerned with the Lorentz transformation which left Maxwell's equations invariant, but was apparently uninterested in the Michelson–Morley experiment on Earth's drift through a luminiferous aether. Conversely, Einstein was awarded the Nobel Prize for explaining the photoelectric effect, previously an experimental result lacking a theoretical formulation.

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  1. F

    From software development to physics PhD

    Hi there, Last June 2019 I graduated with a First class honors in Theoretical physics from one of the Top Unis in the UK. Then I started working for a company (of good prestige) as a software engineer full time. However, a few months in, I decided to apply for Masters and start a side project...
  2. T

    Nolting Theoretical Physics 1, Jacobian Notation Question

    On Page 406 of Nolting Theoretical Physics 1 he has the following notation for the Jacobian determinant $$\frac{\partial( x_{1}, x_{2})}{\partial (y_{1}, y_{2})} = \begin{vmatrix} \left (\frac{\partial x_{1}}{\partial y_{1}} \right )_{y_{2}}& \left ( \frac{\partial x_{1}}{\partial y_{2}}...
  3. E

    Programs Masters then PhD in theoretical physics: Cambridge vs EU?

    Hello, this is my first post. So sorry for the long read in advance. I will graduate from Part II mathematical tripos this year, and I'm currently having a hard time deciding where to go for my Master: For now, I'm definite that I want to do theoretical physics PhD (gravity, cosmology, or...
  4. N

    Math Switching from Electrical Engineering to Theoretical Physics

    Hi all, I'm going to graduate this May with a degree in Electrical Engineering. While I've done pretty well, my passion was never in EE and I'd like to aim for graduate school in Computational Neuroscience. When I look at the background and methodology employed by many favorite (current)...
  5. Q

    What's the timeline for theoretical physics PhD admissions in the UK?

    If I haven't heard back as of yet, does that mean that I haven't been shortlisted? When are interviews usually held and when do people usually find out? My feeling is that if I haven't heard back from the universities as of yet, I haven't been shortlisted but I'm hoping someone more...
  6. I

    Career advise: theoretical physics PhD?

    When I was studying the bachelor in physics, I was happy and got good marks (not the best, but good). I always liked the more theoretical and mathematical subjects. Then I did a masters in Theoretical Physics in Spain. At the beginning I was happy: all subjects were hard but interesting. I spent...
  7. Pispi Choudhury

    Courses Pursuing Theoretical Physics Research: What Courses to Take

    I just finished my sophomore year of a 4-year undergrad in Physics, what relevant courses should I take to pursue my career in theoretical physics research? Advanced grad courses are to be recommended too, thanks.
  8. warhammer

    I Is Theoretical Physics Progressing Slower Than Experimental Physics?

    In respect to the above question, I also have a follow up question. Is progress in Theoretical Physics somewhat slow currently as compared to Experimental Physics?
  9. M

    Potential functions for separation and isochronic gauges

    Most potentials in physics are expressed as a radius or another geometric norm/gauge. I am looking to understand the significance of the choice of potential functions for force/pressure separation in harmonic analysis before this creates a topology. To my understanding this is the decision of...
  10. starstruck_

    Determine the singularity type of the given function (Theo. Phys)

    NOTE: Was not sure where to post this as it is a math question, but a part of my "Theoretical Physics" course. I have no idea where to start this and am probably doing this mathematically incorrect. given the function f(z) = cos(z+1/z) there should exist a singular point at z=0 as at z = 0...
  11. Dingleberry

    Courses Don't enjoy studying theoretical physics

    I'd like to start by saying I don't know if this is the right place to post this, but I feel this community will be able to help me more than any other regarding my issue. I'm an Irish student currently studying undergrad theoretical physics in Trinity College Dublin. Growing up, I was somewhat...
  12. K

    Physics How to do research in theoretical physics or math?

    Hello! All of my undergraduate research so far was in experimental fields, mainly because most of my professors are doing that at the university. The few ones who are doing something more theoretical are mainly working on numerical simulations. I have always been fascinated about theoretical...
  13. W

    Theoretical Physics: Learning to make simple mathematical statements

    Hi all, I am currently involved in a theoretical physics project and would like some advice. One of the main takeaways I hope to (well,) take away is the capacity to make simple physical/mathematical statements that are valid, which seems to be an important part of theoretical physics. How do...
  14. P

    Physics How risky is doing a PhD in theoretical Physics?

    Hello everyone! Apologies if this question has been asked and answered before, please feel free to direct me to that post and delete this one, if needed and if it has been asked before and this post is, hence, redundant. I looked up some of the earlier posts such as...
  15. M

    Programs Module Choice advice for a theoretical physics degree (Durham)

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  16. FourEyedRaven

    Classical How outdated is "Theoretical Physics" by Georg Joos?

    Hi How outdated is "Theoretical Physics" by Georg Joos? I know the quantum mechanics and the nuclear physics sections are obsolete. But what about the statistical physics and the electromagnetism in matter? They look old, but are they obsolete? Cheers 4ER
  17. cordless03

    A Can Particle Physics Revolutionize Biology?

    Are there any ways particle physics can impact biology? Specifically, being able to use methods from theoretical physics to study biological systems (possible physiology related).
  18. STasnim12357

    Schools How good is the Theoretical Physics MSc course at Queen Mary?

    Hello am currently an undergraduate student. My major is CSE. But I am very much interested to do my masters and then PhD in theoretical physics/mathematical physics. Is there any university that admits CS graduates for these courses? I have looked up some universities that offer these courses...
  19. M

    What avenue of physics can a scientist in the Star Wars galaxy study?

    What I’m looking for is some new avenue of physics for a scientist in the Star Wars galaxy to be studying. They probably know what dark matter and dark energy are since Starkiller Base is powered by it. I’m sure they know about how the universe began, why it’s expanding and what it’s fate is...
  20. P

    Testing Physics GRE or Math GRE for theoretical physics?

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  21. Replusz

    Other Looking for ideas for new theory

    Dear All, I am a second year Natural Sciences (the course incorporating the Physics courses) student at the University of Cambridge. I definitely want to specialize in Theoretical Physics next year, but the years spent at University, and the time in the vacations between terms, seems so long...
  22. FourEyedRaven

    Other Errata for Greiner's Series on Theoretical Physics

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  23. J

    Courses Which Abstract Algebra Sequence is Best for Aspiring High Energy Physicists?

    My university offers two different two-semester sequences for learning abstract algebra, and I can't decide which one would be better for me, a physics major. Here are the two sequences and their course descriptions, copied and pasted from the university website: Algebra 1: Theory of groups...
  24. G

    Schools From theoretical physics master to 2nd year grad school

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  25. G

    Schools Theoretical physics university climbing

    I'm a 4th year MPhys student currently finishing my undergrad. I will be attending a theoretical masters course next year at Kings. I have been declined by Imperial and Cambridge so I have started to get a little worried about my future. Even though I have been declined this year, is there any...
  26. Ellegal

    Schools Top School, Low GPA, Good CV -- Grad School for Theoretical Physics?

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  27. L

    Job Skills Theoretical vs Experimental Physics -- which is more glamorous?

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  28. A

    Other How did you find your reasearch area in theoretical physics?

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  29. A

    Programs Medical physics vs theoretical physics

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  30. S

    B Big Rip Theory & Black Holes: Relativity Explained

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  31. K

    Chemistry Chemistry textbook for Physicists

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  32. George Keeling

    News What do theoretical physicists do?

    I took great comfort reading a New Scientist article on the Perimeter Institute, Canada where top theoretical physicists pass the day. They asked four how they get through the day. Two replies gave me great comfort: Asimina Arvanitaki I spend most of my time being confused about things and...
  33. S

    I Interpreting SM Lagrangian "differential particle" terms

    The Standard Model Lagrangian contains terms like these: ##-\partial_\mu \phi^+ \partial_\mu\phi^-## ##-\frac{1}{2}\partial_\nu Z^0_\mu\partial_\nu Z^0_\mu## ##-igc_w\partial_\nu Z^0(W^+_\mu W^-_\nu-W^+_\nu W^-_\mu)## How should one interpret the "derivative particle fields" like...
  34. LilyWillows

    Physics Employability with a degree in theoretical physics vs physics

    Hi! I'm currently in my second year of a five year integrated masters degree in physics. When applying, I chose to study just plain physics as I didn't really know what I wanted to do and I didn't want to limit my options. However, for the past year and a half, and honestly before that too, I've...
  35. Brian Leist

    Admissions How to enter theoretical physics with astronomy background?

    Hi all, I am interested in advancing my education in theoretical physics, specifically topics concerning quantum field theories and quantum gravity. However, I have a somewhat rocky background as an early undergrad and while my Master's degree was achieved with great success in the classroom...
  36. T

    Courses Math as a substitute for theoretical physics

    I was watching a video about physics that said people who want to study theoretical physics but do not want to study things like electromagnetism, thermodynamics, experimental physics, etc, should study math, then take some classes in theoretical physics. This way, you could study your favorite...
  37. T

    Programs Should I Major in AI or Theoretical Physics for a Lucrative Career?

    I am a 12th grader and I am having trouble choosing what I want to major in. My biggest interest is string theory/ quantum field theory/ theory of everything/ particle physics (math intensive theoretical physics). But the problems with getting a physics degree are 1) getting a phd takes a long...
  38. Auto-Didact

    A Taxonomy of Theories in Theoretical Physics

    It goes without saying that theoretical physics has over the years become overrun with countless distinct - yet sometimes curiously very similar - theories, in some cases even dozens of directly competing theories. Within the foundations things can get far worse once we start to run into...
  39. astroman707

    Courses Academic Preparation for gravitational wave careers?

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  40. astroman707

    Programs Difference between an astronomy and astrophysics PhD?

    Is there really much of a difference between an astronomy PhD and an astrophysics PhD? There seems to be a lot of overlap in the fields, and it seems that both can qualify you for many of the same careers, it just depends on the PhD focus. For an example, I'm very interested in almost all areas...
  41. A

    I Is the universe spherical and shaped like a bubble or is it flat?

    Could the universe have been created by the collision of two older universes with the same dimensions? Could the expansion we observe be caused by these two universes still merging like boubbles coming together and the resulting increase of gas makes the film grow larger?
  42. Y

    Courses Should I take advanced courses as a physics undergraduate?

    I am a third year undergraduate physics student with some interest in theoretical physics. This term I want to learn General Relativity or Group Theory, but they are all hard, time-consuming courses. If I don't take them, I can explore broader areas of physics to make a decision on what I will...
  43. S

    Other First year PhD in theoretical physics

    Hello! What can a first year PhD student (in an American university) do, research related, in the field of Theoretical (mainly high-energy) physics? I know in the USA you need to start research from the first semester of PhD (even if you formally choose a definite field of research at the end of...
  44. astroman707

    What math is used the most in cosmology/astrophysics?

    Considering one is taking all the required math courses for a typical physics degree, what math electives are most crucial to the field of cosmology/theoretical astrophysics? Also, is it true that mathematical modeling courses(discrete and dynamical modeling across physics) are more important to...
  45. S

    Other Math tricks for Theoretical Physics

    Hello! Is there a book (any kind of written collection) about mathematical tricks for complex problems (in both math and theoretical physics). Over time I have encountered several nice and impressive tricks to simplify apparently difficult problems and I was wondering if someone gathered them in...
  46. I

    Programs Which Graduate Program in Theoretical Physics is Right for Me?

    Hello. I'm currently studying theoretical physics and planning to continue my study in theoretical physics. I know that there are two interesting places to pursue the education in this field, the International Center for Theoretical Physics (pre-PhD program), and the Perimeter Institute for...
  47. A

    Theoretical Physics should belong in the math department

    Theoretical Physics should belong in the math department to then collaborate with the physics department on new mathematical theories within physics. I can't accept that theoretical physics could really be considered a branch of just physics. I can only see theoretical physics being 95% math and...
  48. SJay16

    Courses Theoretical Physics or Optics?

    I was just wondering which out of the 2 courses would be more beneficial for me as I am interested in Astronomy, Astrophysics, and Cosmology: A senior level course in Optics or a Senior Level course in Methods of Theoretical Physics (Presumably mathematical methods). Course Descriptions...
  49. Alex Petrosyan

    Physics Getting into theoretical Physics after multiple setbacks

    Hi all, I'm a theoretical physics hopeful, and I've had a couple of major setbacks in my undergraduate studies. I'm thinking of whether I should pursue a career in TP, or reconsider doing physics entirely. My background: I've always had an interest in Physics. I got a bronze medal from...
  50. H

    Courses PhD in theoretical physics vs material science?

    Hello PF, I am currently pursuing my Masters in Physics with specialisation in material science. But I am interested in quantum mechanics and want to do PhD and then research in quantum mechanics. But in today's date is it good to go for theoretical physics rather than going for some...
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