Can a theoretical physicist do multiple fields?

[FuturePhysicist]

Based on what I have learned, I know that a theoretical physicist has to work in a specific field. But can one work in two? For instance, a person who has a PhD in cosmology but is working on both cosmology and field theories (quantum, unified). Or maybe even the same person working at a university in a cosmology research department. Conducting research on something like the origin of dark energy, but then personally working on something like quantum field theory. Would it be reasonable to wast time getting multiple PhD's? Or should they just get one in cosmology and read books their other fields. (I'm personally a fan of Dover, so I would be reading their books). Can a person that is fully committed (that is also highly intelligent) get a PhD faster than normal, opening the opportunity for perhaps another one? Sorry about all of the questions, but I am interested in multiple fields of theoretical physics.

 

[mfb]

There is some overlap between cosmology and quantum field theory, with scientists working on topics that have elements of both.
Two completely different fields without overlap? Probably not a good idea (unless you find some new overlap, then it could be amazing ;)). You'll spend a lot of time just to keep up with the research of others, doing that in two fields at the same time will reduce the time you can spend on your own research.

Would it be reasonable to wast time getting multiple PhD's?

No. And it would look odd: "why did you go for another PhD position instead of getting a post-doc position (same tasks, better salary)? What went wrong?"

Or should they just get one in cosmology and read books their other fields.

To get into the most recent developments, books won't be sufficient, but they are a good start.

 

[cgk]

Some people work in multiple fields, but this usually takes the following form:
(1) Person P is an expert in the (theoretical) technique X
(2) Technique X was developed in field A.
(3) Technique X is also useful to solve a problem in the distinct field B.
(4) Person P applies technique X to field B.

This still requires substantial effort, as the translation is normally not one-to-one, and one needs to establish both proficiency and credibility in field B in order to make meaningful contributions which are also taken up by B's community. I am aware, for example, of transfers of many-body quantum mechanics techniques from nuclear physics to quantum chemistry (and back, e.g., the Coupled Cluster method), or from quantum chemistry to condensed matter theory and back (e.g., algorithms for exact diagonalization). There have even been examples of numerical techniques which have been developed in chemistry or physics fields and subsequently picked up by mathematicians and from there exported elsewhere (e.g., Davidson-Jacobi diagonalization, Matrix-product states/tensor train approximations, or Krylov subspace convergence accelerators like DIIS or GMRES, etc.).

In any case, one would not do more than one PhD. One can publish in any journal as long as one's contributions are compatible with the journal's standards and practices. But again, in order to make meaningful contributions to multiple fields, one would need substantial expertise in both, and normally also collaborators in the target field who are willing to get one started. Neither is necessarily easy to acquire.

 

[Niflheim]

I definitely wouldn't do multiple PhDs. Many theoretical physicists do work in multiple fields, usually very closely related with overlaps. Obviously, mathematics is an exception to this as many physicists have made huge contributions to math through their work.

As for separated fields, I would focus on one subject until you are financially stable with a good postdoctoral position, and dedicate some of your own time to multiple subjects if you wish. Only true geniuses can get away with doing big things in multiple fields at once (think Newton, Leibniz, etc.)

 

[homeomorphic]

Only true geniuses can get away with doing big things in multiple fields at once (think Newton, Leibniz, etc.)

It's not just a question of genius. In the past, it was possible to know everything there was to know about math or physics. That just isn't the case any more.

 

[DEvens]

The thing to do after one PhD, if you really want to learn about those other things, is get an academic position. There you will be expected to learn about other stuff in addition to doing research. And at a university you will have good opportunity to learn about those things from people who are already quite experienced, even expert.

So a prof in cosmology wants to know about, for example, quantum field theory. QFT contributes to early universe cosmology. So the cosmology guy wanders over (down, up, whatever) to the physics department and finds out who is approachable to teach him about the "good stuff" in QFT. And maybe they write a couple papers together, with one guy answering all the hard QFT questions, and the other answering all the hard cosmology questions. And probably a grad student or two doing all the hard equations.

 

[FuturePhysicist]

With these attributes, would I be likely to succeed as a theoretical physicist? Which ones should I work on to improve?
-Superior Intelligence
-Curious
-Committed
-ADHD (Diagnosed)
-Show OCD-like signs
-Creative
-Shy (at times)
-Like to read but tend to procrastinate with it at times
-Observant
-(I'm Training my cognitive abilities and mental calculations using neuro-plasticity)
-Obsessed with learning new things
-Obsessed with mathematics
-Love physics and somewhat neuroscience and philosophy
-Driven
-Sometimes I become unaware of my surroundings and go into a sort of cognitive thinking state
-I like to challenge (and beat) other intellectuals sometimes
-Tend to like things my way (I confess)
- (Please do not argue or criticize about this statement) Non religious
-I believe in making humanity last almost infinitely. (As in becoming a multi-planet or even multi-universal species)

 

[cgk]

What will decide whether you will be successful in physics (or any other field, for that matter), will be whether or not you are both able and willing to do the work required to become really good in it. The list of properties you gave is no indication of this; it could just as well have come from a horoscope.

Or, to put it more bluntly: If your "obsession with learning new things" distracts you too much from learning the things you need to know, none of your "superior intelligence" will save you. If your "shy (at times)" helps you focus on your work by keeping you away from social distractions in every day situations, but prevents you from seeking help when you need it, or from making essential contacts (e.g., with peers, professors, colleagues at conferences), there will likely be no career for you. If your "tends to like things my way" means that you will not adapt safety procedures in labs, or leads you to ignore important advice, it can get you fired (literally or figuratively, respectively).

Why do you even ask this question? Is this not a matter of introspection? At the very least, you should ask someone who both knows you, and knows what it takes to be a physicist.

 

[FuturePhysicist]

What will decide whether you will be successful in physics (or any other field, for that matter), will be whether or not you are both able and willing to do the work required to become really good in it. The list of properties you gave is no indication of this; it could just as well have come from a horoscope.

Or, to put it more bluntly: If your "obsession with learning new things" distracts you too much from learning the things you need to know, none of your "superior intelligence" will save you. If your "shy (at times)" helps you focus on your work by keeping you away from social distractions in every day situations, but prevents you from seeking help when you need it, or from making essential contacts (e.g., with peers, professors, colleagues at conferences), there will likely be no career for you. If your "tends to like things my way" means that you will not adapt safety procedures in labs, or leads you to ignore important advice, it can get you fired (literally or figuratively, respectively).

Why do you even ask this question? Is this not a matter of introspection? At the very least, you should ask someone who both knows you, and knows what it takes to be a physicist.

Thank you. By the way, I got this list from what other people say, and what I know. Not from that irrational "horoscope" thing. I asked because I currently have no acquaintances or contacts that know what it takes to become a physicist. But once again, Thank you. I will use this information to better prepare myself for the future.

 

[FuturePhysicist]

Okay, so my question here is, If I want a PhD. in a certain field of theoretical physics, which field would be more open to other fields. I was thinking something like mathematical physics, particle physics, or cosmology. Since there are other fields either based off of, or are closely associated with those. Which one would make a greater impact (If I were to make a discovery) to the Theory of Everything or just physics in general. Which one do you learn more in?

 

[mfb]

All fields of physics have a great impact on physics in general.

A unification of quantum field theory and gravity is in the field of particle physics (with some cosmology involved). Note that discoveries are always the work of many scientists. They rarely come out of nowhere, especially in fields like particle physics where every publication relies on hundreds of previous publications for its framework.

 

[ChrisVer]

Okay, so my question here is, If I want a PhD. in a certain field of theoretical physics, which field would be more open to other fields. I was thinking something like mathematical physics, particle physics, or cosmology. Since there are other fields either based off of, or are closely associated with those. Which one would make a greater impact (If I were to make a discovery) to the Theory of Everything or just physics in general. Which one do you learn more in?

Right now, I don't think you can find any the Theory of Everything in either cosmology or particle physics. It's still very far from experimental verification [from both cosmology+particle physics the only thing you can take is "evidence" ]. In general the "Theory of Everything" is still in mathematical form and constructions, for dealing with its problems.
In general cosmology+particle physics is a worthy PhD (if you ask me) exactly because there is a huge overlap between them in the recent researches and it is the "next goal" (after closing SM with the 1 Higgs if its CP is measured to be the right one) for the future experiments - at least that's what I "feel" in the air around me.

 

[MathAmateur]

With a PhD in theoretical physics you will be welcome in just about any technical field. There are people with Theoretical Physics doing all kinds of things from software to aerospace navigation to, well, theoretical physics. The reality is the vast majority of people who receive PhDs in theoretical physics end up working for the likes of me doing engineering, others do biology, others linguistics and others, believe it or not and I have seen it, teaching theology. Don't worry about it. Get your PhD. Have fun. The worst you will do is end up working for me. We are hiring 76 software engineers this year and we want a number of physics graduates included -- BS, MS or PhD in whatever specialty.

 

[homeomorphic]

With a PhD in theoretical physics you will be welcome in just about any technical field.

I'm not so sure about that. For example, ParticleGirl had to work as a bartender for a year. This is a bigger risk if you do less practical stuff (particle physics, cosmology, ) or if you don't do a lot of programming in grad school.

The biggest danger is to be over-confident that everyone will be in awe of your PhD and be eager to hire you because if you are over-confident, you may be unprepared. At least I can say with certainty that there will be very few job postings that you'll fit into hand in glove, unless you have prepared specifically for them.

Maybe people are in awe of my PhD (in math), but it's not the sort of awe that inspires many people to want to hire me. It's more like, "wow, what an achievement, but you don't have the skills we need here" or "what is a PhD doing talking to us?"

Particularly, I hear over and over again from software people that they want you to have either a degree or prior experience. I'm sure there's someone out there who will hire most PhDs in math and physics, even including me, but it's a needle in a haystack. The good news is that, yes, there is a needle in the haystack. The bad news is that it's a haystack. For someone who is not good at job search type stuff, this could be a serious reason to not get a PhD (there are other reasons). But the more serious danger is not being ready for the job search because you think it's going to be easy. That's what's going to really make you end up like me.

 

[Ben Niehoff]

If you want to have the flexibility to apply your theoretical physics PhD anywhere outside of academia, then you had better develop additional skills. Learning some actual computer programming in a language like C/C++ or Fortran can be valuable, and such skills often line up with physics research if you do things like numerical simulations. However, be warned that it is common knowledge in industry that programmers who come out of academia with a science degree rather than a software degree are likely to be terrible programmers who learned on-the-fly how to hack together a simulation, but don't really know the ins and outs of what they're doing in software. I don't know of any physicists who can do things like design databases, web applications, etc., which is the kind of thing that is most useful in the real world. It might help to take some CS courses, both to learn properly, and to document that you've learned something properly.

Within academia, I think it's pretty common for people to branch out into neighboring fields; in fact, finding a novel way to combine ideas from different fields will probably make you famous. But you will need to be a bit established in your own field first.

There are lots of people working on combining ideas from condensed matter theory, quantum information theory, cosmology, QFT, and string theory. They come in from various directions...focus on doing well in one field during your PhD, and make sure to make lots of friends and keep tabs on what is happening in other fields.

 

[Arsenic&Lace]

I'm not so sure about that. For example, ParticleGirl had to work as a bartender for a year. This is a bigger risk if you do less practical stuff (particle physics, cosmology, ) or if you don't do a lot of programming in grad school.
.

That's pretty weird, I was getting beer with some particle physics students/graduates at my institution which is somewhere in the 40's as far as rankings go, and they all were bragging about having offers or jobs in finance shortly after graduating. Apparently financial institutions like analytical/theoretical knowledge as well as programming; the sweet spot is a little bit of both.

To the OP, I'd steer clear of cosmology/particle physics if I were you, there does not appear to be very much good science going on in those fields these days.

 

[mfb]

To the OP, I'd steer clear of cosmology/particle physics if I were you, there does not appear to be very much good science going on in those fields these days.

How did you get that impression? As a particle physicist I'm certainly not neutral, but a lot of great science is done there. And in terms of scientific rigor, I'm still waiting to find another field that is as accurate as experimental particle physics.

 

[Arsenic&Lace]

How did you get that impression? As a particle physicist I'm certainly not neutral, but a lot of great science is done there. And in terms of scientific rigor, I'm still waiting to find another field that is as accurate as experimental particle physics.

Oh there are still plenty of rigorous, pragmatic particle physicists left in the world, but some of the dominant trends in contemporary theory, as far as I can tell, seem to be flimsy philosophy and pure mathematics rather than physics, a consequence of the lack of good experiments. Much of the particle physics I hear about from colleagues which seems reasonable to me appears phenomenological in nature which presumably is not what the OP is interested in, and at any rate such subfields are likely saturated and matured, which are not qualities that are amenable to young scientists. Quantum gravity in particular neither has a healthy phenomenological component or far more importantly even a basic experimental component, which relegates it outside the realm of scientific inquiry for the time being, unless the OP is astronomically talented and can coax accessible empirical predictions out of that perilous subject.

The abnormal accuracy of particle physics is an artefact of fundamental nature of the objects it studies I would wager, although this accuracy is hardly ubiquitous to the field; in a brief stint at a nuclear physics lab I became well aware of the severe challenges associated with predictions in QCD.

 

[mfb]

Oh there are still plenty of rigorous, pragmatic particle physicists left in the world, but some of the dominant trends in contemporary theory, as far as I can tell, seem to be flimsy philosophy and pure mathematics rather than physics, a consequence of the lack of good experiments. Much of the particle physics I hear about from colleagues which seems reasonable to me appears phenomenological in nature which presumably is not what the OP is interested in, and at any rate such subfields are likely saturated and matured, which are not qualities that are amenable to young scientists. Quantum gravity in particular neither has a healthy phenomenological component or far more importantly even a basic experimental component, which relegates it outside the realm of scientific inquiry for the time being, unless the OP is astronomically talented and can coax accessible empirical predictions out of that perilous subject.

The abnormal accuracy of particle physics is an artefact of fundamental nature of the objects it studies I would wager, although this accuracy is hardly ubiquitous to the field; in a brief stint at a nuclear physics lab I became well aware of the severe challenges associated with predictions in QCD.

Wait, the parts without phenomenology are bad because they lack experimental predictions ("flimsy philosophy and pure mathematics rather than physics"), and the parts with phenomenology are bad because they are established and get tested in experiments?

The accuracy of particle physics experiments is certainly an achivement of its analysis methods, and the theory predictions are very nice as well, with very few errors in them despite the large number of ways to be wrong.

There was some data to the effect that 15-30%, depending on the market, of new physics PhDs don't have a job lined up at graduation. And you have to realize that a large percentage of the people who DID get jobs got postdocs.

According to the American Institute of Physics, for new PhDs in 2011/2012 one year after graduation (source):
56% postdocs, 31% potentially permanent positions, 9% other temporary positions, 4% unemployed

Only 12% of the Postdocs gave "Could not obtain a suitable permanent position" as reason for their choice, 32% "Necessary step to get desired future position"

 

[Arsenic&Lace]

Wait, the parts without phenomenology are bad because they lack experimental predictions ("flimsy philosophy and pure mathematics rather than physics"), and the parts with phenomenology are bad because they are established and get tested in experiments?

The latter point regarding the more phenomenological aspects is with regards to the OP's probable but not yet established disinterest in phenomenology/computational particle physics. There is nothing in either of my posts which suggests in any way that I feel skeptical at all about that aspect of the field. The other problem is that it does not appear to comparatively scientifically or financially active (see: the recent NSF budget).

The accuracy of particle physics experiments is certainly an achivement of its analysis methods, and the theory predictions are very nice as well, with very few errors in them despite the large number of ways to be wrong.

Well the former case was simply a misunderstanding, I was never referring to the analysis performed by experimenters, only the comparison between theory and experiment, which is absolutely a consequence of the nature of the physics and has nothing to do with its practitioners.

 

[Dale]

Several off topic posts have been removed. Please stay on topic.

 

[Mmm_Pasta]

People do work in multiple fields but usually there is some sort of connection. For example: right now I do research in transformation optics which combines general relativity and optics. We are using transformation optics to increase the efficiency that computers perform simulations of light-matter interactions. We investigate the physics of these interactions, development of numerical methods to improve computations, and also look at the underlying mathematics (lots of PDEs). The person I am working under has published papers on optical physics/photonics and numerical analysis (in particular PDEs).

 

[MathAmateur]

I'm not so sure about that. For example, ParticleGirl had to work as a bartender for a year. This is a bigger risk if you do less practical stuff (particle physics, cosmology, ) or if you don't do a lot of programming in grad school.

Maybe. We hire a lot of physics types, but our work is maybe a bit more complex than average. The hardest part of getting a sophisticated degree like particle physics or cosmology is lowering yourself to do the more mundane tasks that us lesser (or less lucky) beings end up doing to earn a living. I think that is why a lot of the people earning PhDs do things like bartending for a while. It is hard to admit that one has to drop into the real life tasks like building aircraft or computers after exploring the Universe. What is really hard is to go through all that work and then end up being paid the same as a BS or MS engineer or less if those people are your boss (which is likely).

 

[mfb]

I think that is why a lot of the people earning PhDs do things like bartending for a while. It is hard to admit that one has to drop into the real life tasks like building aircraft or computers after exploring the Universe.

Building an aircraft is not so different from building a particle detector I guess (never built a real aircraft). Sure, the goals are different, but most of the everyday work is on some small aspect of it.

 

[HiggsBoson1]

A theoretical physicist, while working in a specific field, usually has some knowledge of the others. If as you mentioned, he was working on a theory with quantum physics and cosmology, he would need to research a little about the field, of which he did not know as much. Many physicists who are involved in new theories, know a good deal about fields other than their chosen one.