Theoretical physics Definition and 106 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. K

    Classical Looking for a physics textbook which shows how to develop theory

    I was wondering if there is any such textbook which shows how a real physicist actually goes about developing models and or theories to explain experimental observations. I want to see how it is done in practice. Is there such a book? At a level that an undergraduate can understand. It is great...
  2. S

    I Varying laws of high energy physics in inflation?

    I am have some questions that have arisen while reading an old but interesting article by Andreas Albrecht [1] that cites an article by Andrei Linde in the 90s on cosmic inflation [2]... Albrecht's paper is related to his ideas on "clock ambiguity" in which he proposes that the laws of physics...
  3. A

    How Much Will Sponsoring Physics Research Cost? (Amount to Sponsor Research through a Grant)

    Suppose there is a nonprofit that wants to order a piece of research in theoretical physics. The research is rather small; it consists in considering an issue and writing a 8-10 pages article. The physicist to do the research will be from a high income country; he/she should be an experienced...
  4. PhilipsPhysics

    I Where does Hamilton's Principle come from?

    Hamiltons Principle and the physcial entity action are the terms in which modern physics is formulated. How do you know that you can always find a Lagrangian for a System which is then used for Hamitlons Principle and the formulation of Action? Why is the action stationary?
  5. S

    Is there any physicist doing research who was once an astronaut?

    Is there any former astronaut who is now doing research in theoretical physics (like e.g string theory)?
  6. W

    Studying Physics intrigues me but Math makes more sense. What to study?

    Hi, I have the following problem, maybe someone relates. I am about to finish my Bachelors Degree in Physics and must say it was a very unenjoyable road. I started it because since forever I was fascinated by the "great" ideas trying to explain reality that lie behind physics, i. e. Quantum...
  7. P

    Job Skills Any industry jobs for physics grads requiring no programming?

    Hi all, my question is as title. I am a fourth year PhD student in US and planning to graduate early to get in industry or community college. I major in high energy theory, and I have no coding/simulation skills at all (not interested at all). Thus, my situation is that professionally I have...
  8. S

    Nobel laureates for and against string theory?

    According to Michio Kaku, Nobel laureates have taken both sides towards string theory since some of them accept it and some of them reject it, as he says here ( “Kaku also explains the intense controversy swirling around this theory, with...
  9. W

    How to study Mathematics for Theoretical Physics

    I have a B.S in Mathematics, but wish to pursue Theoretical Physics. I still have a great deal of undergraduate Physics coursework to take before I can apply to graduate programs. My question has to do with the Mathematics that is crucial in order to do Theoretical Physics. Is the mathematics...
  10. andrew0310

    Physics What is it like to do theoretical physics research?

    Hello everybody, I am an undergraduate student studying computer science and I love it, especially Artificial Intelligence. I'm a curious person, so there are a lot of things that I find intriguing. But I sometimes wonder if a physics career would be more interesting, not because I don't like...
  11. 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...
  12. 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)...
  13. warhammer

    I Top Theoretical Physicists

    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?
  14. 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...
  15. 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...
  16. 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...
  17. M

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

    I'm starting at Durham on the 29th of September and I need to get my module choices sorted. I have the choice between 40 credits of maths modules designed for scientists, and 40 credits of maths modules done by regular maths students. They say that you should only do the regular maths modules if...
  18. cordless03

    A High-Energy biophysics?

    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).
  19. 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...
  20. 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...
  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. J

    Courses Physics and Abstract Algebra

    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...
  23. G

    Schools From theoretical physics master to 2nd year grad school

    I would like to ask if anyone has been admitted to a graduate school(US) straight to 2nd year after a theoretical masters MSc degree in the UK. I am asking because I would really like to study in the US, preferably on top universities but I don't want to waste another year taking essentially...
  24. 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...
  25. L

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

    I am worried that I am passionate about physics and yearn for a career in physics(through theoretical physics), and by a career I mean a placement in a prestigious institute and then be part of leading physics, but would that require sacrificing my entire 20s and even 30s or can I can get all...
  26. S

    B Black holes and the Big Rip

    According to the Big rip theory if Black holes tear apart after a very long time, then according to the theory of relativity an object that reaches the event horizon should see time passing infinitelty and by the time the object was swallowed wouldn't the black hole not exist anymore because of...
  27. K

    Chemistry Chemistry textbook for Physicists

    Hello Being a professional physicist(Quantum field theory and HS theory) I'd like to learn chemistry for some reasons. I've already tried to find a nice Chemistry textbook but failed to find physicist friendly one. My last class on chemistry was in high school like 11 years ago already, so my...
  28. 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...
  29. 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...
  30. 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...
  31. 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...
  32. astroman707

    Courses Academic Preparation for gravitational wave careers?

    If someone wanted to pursue a career in gravitational wave physics, and work at places like LIGO, studying astrophysical objects such as black holes and neutron stars, etc. What are some key courses/skills that person should take/learn as an undergraduate, and graduate student?
  33. 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...
  34. A

    I How was our universe created?

    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?
  35. 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...
  36. 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...
  37. I

    Programs ICTP or Perimeter Institute?

    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...
  38. 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...
  39. Jianphys17

    I Relation between statistics and theoretical physics

    Hi at all, maybe it's a bit trivial. However, the question that i ask myself is ; that relation there is between statistics-probab theory & theoretical physics. What role does it play in theoretical research ? (apart from the probabilistic amplitudes encountered in qm) Thanks for the answers
  40. assademre

    Where to start with Theoretical Physics?

    Firstly, I'm sorry if it is wrong part to start this thread. I'm new here and I can change the category if you let me know. Secondly, I want to learn something about theoretical physics. I am about to finish my study Mathematics in a semester. However, I consider to study physics either and I...
  41. Hypercube

    Physics What do theoretical physicists actually do?

    Dear PF community, I was wondering, what do theoretical physicists actually do? Putting teaching and marking responsibilities aside, would you be able to describe to me your day-to-day activities when you do research? It is something that has been on my mind for a while. I suspect PF members...
  42. astroman707

    Schools Is New College of Florida good for physics?

    I'm wanted to go into theoretical astrophysics/cosmology in grad school, and I'm look for schools that will look very good to graduate admissions, and that will give me a great preparation. New College seems to have exceptional results in sending students to top grad schools according to their...
  43. F

    Physics The right physics field for me

    I have finished my masters degree in cosmology and my research was on inflation, despite it being interesting, I'm not really fond of doing simulations/computations using a computer for a very long time. Don't get me wrong, I know that every physicists should know at least some computational...
  44. A

    I Principle of superposition of states

    Upon reading Landau QM, the Principle of superposition of states, I got confused. It states (and i quote): "Suppose that, in a state with wave function Ψ1(q), some measurement leads with certainty to a definite result 1, while in a state with Ψ2(q) it leads to a different result 2. Then it is...
  45. P

    Programs Physics engineering Or Applied Physics? ....theoretical?

    Hey there. I am going to stay the University next year and I want to know what do you think about the three options I have actually. I really like science, and I like to know about the process of the nature, how it is defined by math and by the physical processes. It is my passion I, in the...
  46. Q

    Programs Master in theoretical/mathematical physics. Guidance.

    Hello, I was wondering if you could give me some advice on what master’s degree or which specific master courses I should take. I am a physics student and I am going to finish my bachelor in physics next year. I plan to do a master in theoretical physics or in mathematical physics. However I...
  47. C

    Programs To pursue a masters degree in theoretical physics

    Hello, I'm about to start my last year of bachelor degree in physics, and in a few months I would like to have a clear idea of where I want to go for my master degree. My dream since I started university is to pursue theoretical physics, in which specific field, that remains for me to...
  48. G

    Best Written High School Physics Text Books (SAT)

    Advanced Physics (Advanced Science) by Steve Adams & Jonathan Allday from OUP Oxford: and Physics (Collins Advanced Science) 3rd Edition by Kenneth Dobson from Collins Educational: Does anyone know any of these books? I find them very...
  49. Z

    I Dark Matter Interactions

    As I have come to understand it - we have no current means of directly interacting with Dark Matter. We can only observe the gravitational effects that Dark Matter has on Baryonic Matter. My question is: What forms of detection have been attempted and determined to not directly interaction...
  50. Eslam100

    Other What are the topics in theoretical and mathematical physics?

    I'm a rising physics sophomore at a Japanese university. I've studied general physics, linear algebra, and analysis (actually, calculus of single and several variables with emphasis on analysis, everything was proven and the theoretical background was well explained) Other than that, I've...