What is Theoretical physics: Definition and 535 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. M

    B How would physics change if Planet 9 were a primordial black hole?

    I watch John Michael Godier on YouTube. He is a futurist and makes fantastic videos where he speculates on many things. Todays video was about primordial black holes and he speculated about Planet 9 not being visible because it may actually be a black hole born in the dawn of the universe. He...
  2. H

    Other Need advice regarding choosing my master's research project in theoretical physics and applied maths

    Hi, I am pursuing a master's in theoretical physics and applied maths and now I need to start working on a research project. It has been so tough to decide the topic as I currently don't feel ready to commit to one particular research area. Based on the modules I have taken so far, I do get...
  3. DanielcoderX

    Seeking insights on careers in theoretical physics and cosmology

    TL;DR Summary: Aspiring physicist seeking insights on job prospects, education paths, and salaries in theoretical physics and cosmology. Share your experiences and advice for informed decision-making. Thanks! Dear members of the forum, I'm currently in Grade 11, seeking insights on...
  4. W

    Other What are areas of research that pertain to Grand Unified Theory?

    I am planning on pursing a Phd in Theoretical physics or Mathematical Physics in the next several years. My main motivation is doing research when it comes to grand unified theory. What areas of research (within that umbrella, in a theoretical sense) should I start looking into that are at the...
  5. jv07cs

    Programs REU Opportunities for International Students in Theoretical Physics

    I'm a physics undergrad student in Brazil and I'm about to finish my sophmore year. I'm really interested in computational and theoretical physics and I'm currently in the beginning of this year long research project with a professor in my university on the study of the 3+1 spacetime split of...
  6. Q

    I Why is Photon Energy Quantized in Terms of Sine Wave Frequency?

    Hello everyone, I've been grappling with a concept for years, diving into internet resources and pestering professors, yet I still find myself tangled in confusion. I'm reaching out in hopes that someone here can shed light on a question that has been haunting my thoughts regarding the nature...
  7. C

    Prospective ArXivLabs project

    In short, I'm interested in working on a web-app to make landmark papers in theoretical physics and mathematics more broadly accessible, especially to undergraduate and graduate students who are looking to catch up to modern topics (without sacrificing rigor or exactness of understanding), and...
  8. W

    What are decent to good graduate Physics Programs in the UK?

    Other than well known institutions such as University of Cambridge and Oxford. What are grad programs that are worth considering for a Phd? I am still narrowing down my niche, but I am interested in Theoretical physics, Mathematical Physics, and high energy physics.
  9. Demystifier

    I Two approaches to science

    As you may have noticed, I am obsessed with understanding the difference between two views of quantum mechanics, one of which can be called the "standard" view, and the other the "realist" view. The difference, of course, is very complicated, but I believe that the essence and origin of the...
  10. G

    I can't find a PhD in theoretical physics after 6 months of trying

    Hi, I am 25 years old living in EU. I am posting my experience with the objective of getting advice or opinions. I have a bachelor in physics with a thesis on the SM electroweak sector. I have a master again in theoretical physics with a specialization on Hadron Physics ( QFT ). Both of my...
  11. harutsuki

    I think I ended up in the wrong Laboratory? (Theoretical Cosmology)

    TL;DR Summary: I dont enjoy my lab subject. I am currently in grad school (not US) and in the theoretical Cosmology laboratory, however I feel like I ended up in the wrong side. I did undergrad research project in astrophysical data simulation and thought that this is what I want to do in...
  12. Ahmed1029

    Should I submit an outlandish physics idea that feels right?

    I'm curious to get people's opinions about whether this is interesting enough to write up for submission. I arrived at a set of coordinate transformations that are different from the Lorentz transformations, but which produce a coherent mechanical framework. It gives a very beautiful physical...
  13. S

    Deciding between physics and mathematics

    I am not sure if this is the right place to post this, so if not sorry in advance. I am a second-year physics major, thinking of switching to mathematics. I have always been interested in both, but I could never be sure whether I could become a mathematician. Understanding physics was...
  14. Whitestar

    Exploring Theoretical Physics: Math Requirements and Resources

    Hello. I have been a member on this forum for quite some time and I came here because I've always had an interest in science, particularly physics. When I was in Junior High, I did very well in my science class but by the time I got to college, I wanted to make money. However, I realized that...
  15. A

    Programs Advice for majoring in theoretical physics

    I am going into my senior year of hs next year and I am meditating on what I should major in. I have a keen interest in physics but also a love of math. The field in physics I would like to major in is theoretical physics/astrophysics, and the pure maths I am interested in are diff, algebraic...
  16. modellatore

    Studying Theoretical Physics Study Path (it's about tetrads....)

    I'm a graduate theoretical physics student at the (almost) end of his master's degree with a fairly varied curriculum, as I attended both QFT (and sub-courses on qed qcd etc) and GR courses. However in my latest intro to quantum gravity classes I familiarised with tetrads and, after a lot of...
  17. A

    Other Transitioning from Theoretical Physics to Software Dev: Steps & Difficulties

    I'm going into my final year of undergraduate theoretical physics. I have had a bit of a deviation in what I want to do and would really like to work in software development in the future. How difficult would it be for me to deviate from my current position and what steps should I take to to...
  18. Admiralibr123

    Physics Quantum Computing masters with Theoretical physics background

    I want to do a masters related to quantum computing from a physics background and my criteria for the place is: 1. A quantum computing group with experimental realizations and industrial ties. 2. A strong theoretical physics department with research in fundamental physics 3. A good chance of...
  19. 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...
  20. 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...
  21. Jamestein Newton

    Can one do mathematical physics and theoretical physics at the same time?

    I finished my 1st-year physics, took analysis, linear algebra, mathematical logic, classical mechanics, quantum mechanics(I was exempted from intro phy and took some 3rd-year physics courses) I internal transferred to pure maths. The reason is that the curriculum of the physics programme in our...
  22. Jamestein Newton

    Courses Is it necessary for theoretical physics students to take a course in PDE?

    By PDE. The book written by Walter Alexander Strauss perfect described a typical undergraduate PDE course I have in my mind. It should at least include: Laplace equations, waves and diffusions reflection, boundary problems, Fourier series The content of the book I mentioned can also be found...
  23. A

    Grant for Research in Theoretical Physics

    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...
  24. OscarV

    Calculus Should I read Spivak's Calculus as an undergrad in theoretical physics?

    I am about to start a physics with theoretical physics major, I've taken calculus before but I've not been satisfied with the "memorization of formulas" type books. I started to read Spivak and found it enjoyable, but since it's a major undertaking I am also concerned for the practical value...
  25. ergospherical

    Applied Lectures on the geometric anatomy of theoretical physics

    I stumbled across this series of 28 lectures by Dr Frederic Schuller of the university of Twente whilst searching for lectures about Lie theory. Having watched through lectures 13 to 18, I think they are simply superb (of course I'm assuming the rest are of similar quality). I only wish he would...
  26. George Jones

    Exploring Chris Isham's Work in Theoretical Physics

    An interesting article about theoretical physicist Chris Isham (by Michael Duff) has been posted on the arXiv, https://arxiv.org/abs/2112.13722 Combine this with (from "Group Theory for the Standard Model of Particle Physics and Beyond" by Ken Barnes) Isham has written two books that I quite...
  27. 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?
  28. 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)?
  29. 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...
  30. Monsterboy

    Do you agree with Jeff Bezos on theoretical physics?

    I recently watched a video of Jeff Bezos explaining his journey from Princeton to Amazon. (watch from 24:39) He said when it comes to theoretical physics, if you are not in the top 50, you are probably just wasting time. How accurate is this opinion ? Are most theoretical physicists just...
  31. M

    Programs Maths vs Physics degree for theoretical physics

    Hi, I'm interested in doing research in theoretical cosmology (the kind or work hawking did). Should I do an undergraduate degree in mathematics or physics? I'm in the UK so I can't do a double major. I'm well aware of the fact that interests change a LOT later on, but ideally which one is...
  32. Hamiltonian

    Relativity Advanced Theoretical Physics: a book on SR & GR for Undergrad Students?

    I recently came across a book called advanced theoretical physics -nick lucid. chap6 covers tensors and chap 7&8 cover SR&GR. I have studied a bit of SR before but never GR. At this point in life I don't want to read huge books on the subject. this book covers relativity entirely in three...
  33. 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...
  34. 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 (https://www.snowboundbooks.com/book/9780385542746): “Kaku also explains the intense controversy swirling around this theory, with...
  35. T

    Programs PhD Theoretical Physics - Part 2

    Hello, I have several questions around the application process as well as the organization. 1. Are you aware of any reference website centralizing PhD offers by countries? 2.When it comes to the organization/management/ supervision of a PhD program, I wonder if there are differences by...
  36. E

    Other Your thoughts about "International Journal of Theoretical Physics"

    A year ago, I asked a question about two journals, both of which were predatory ( https://www.physicsforums.com/threads/are-open-access-journals-legit-for-my-cv.990744/ ). Thanks to the overwhelming advice I have received, I did NOT publish in either of those journals. Right now I am asking a...
  37. Falgun

    Studying Computational Skills for Theoretical Physics

    I am currently learning to code by auditing Harvard's CS50 course on edx. I am mainly interested in pursuing a theoretical physics major in the future. What I would like to know which scientific computing software/language (as in OCTAVE, SCILAB, FORTRAN, JULIA, etc ) can I learn alongside which...
  38. rhotonsix

    I Pure mathematics problem solving and relevance to theoretical physics

    I am recreationally self studying physics and math with the ultimate goal of understanding theoretical/mathematical framework of classical mechanics, general relativity, and quantum mechanics (in addition to the actual physics). The question I have is how deep in the realm of pure math does one...
  39. T

    Programs PhD Theoretical Physics (study, application & all sorts of guidance)

    After graduating with 2-years Masters in TP, I wish to return to academia by undertaking a PhD in theoretical physics and I have A LOT of questions since I am aware that it is a, extremely competitive area especially when you were out of the game for a while, about 5 years for me… What are the...
  40. 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...
  41. 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...
  42. K

    A Differential Forms or Tensors for Theoretical Physics Today

    There are a few different textbooks out there on differential geometry geared towards physics applications and also theoretical physics books which use a geometric approach. Yet they use different approaches sometimes. For example kip thrones book “modern classical physics” uses a tensor...
  43. w4y021

    Courses Changing my life from Engineering to Theoretical Physics

    Long times have been that I've decided changing my job from engineering to theoretical physics. Because I don't want to learn the rules that have been discovered by any scientists and make a situation about getting it real :]. I want to learn how the rules of nature is being discovered and what...
  44. 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...
  45. 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}}...
  46. 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...
  47. 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)...
  48. 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...