Gold Member

## Main Question or Discussion Point

Hey!

I am about to start my Bachelor's thesis about General Relativity. My professor mentioned that my thesis might as well be related to Gravitational Waves. Do you think that it would be appropriate to work on Gravitational Waves for a Bachelor's thesis? Isn't it too advanced?
Also, any idea on what part of Gravitational Waves I could discuss?

jedishrfu
Mentor
Since its for a BS then how about how they traverse spacetime and how LIGO has successfully detected them. Other ideas could be how they are formed and their properties.

https://en.wikipedia.org/wiki/Gravitational_wave

As an aside:

Also one common issue is peoples conflation of gravity waves vs gravitational waves. They are separate phenomena. Here's a link for reference on gravity waves so you can see the difference

https://en.wikipedia.org/wiki/Gravity_wave

Gold Member
Since its for a BS then how about how they traverse spacetime and how LIGO has successfully detected them. Other ideas could be how they are formed and their properties.

https://en.wikipedia.org/wiki/Gravitational_wave

As an aside:

Also one common issue is peoples conflation of gravity waves vs gravitational waves. They are separate phenomena. Here's a link for reference on gravity waves so you can see the difference

https://en.wikipedia.org/wiki/Gravity_wave

So this paper is actually about gravitational waves, and not gravity waves, right?

DrSteve
Gold Member
Hey!

I am about to start my Bachelor's thesis about General Relativity. My professor mentioned that my thesis might as well be related to Gravitational Waves. Do you think that it would be appropriate to work on Gravitational Waves for a Bachelor's thesis? Isn't it too advanced?
Also, any idea on what part of Gravitational Waves I could discuss?
In my opinion a descriptive thesis that avoids math would be uninteresting. On the other hand, if you could say something about how GR gives rise to propoagating waves, as in https://en.wikipedia.org/wiki/Gravitational_wave#Mathematics
Are you comfortable with that level of math?

haushofer
I'd think it's a suitable topic. I followed GR in the beginning of my third year, and this opens up a lot of interesting topics for a bachelor thesis.

In that direction it could be interesting to dive into linearized GR (= Fierz-Pauli theory), how gravitational waves emerge from such a linearization, and if you want to knot it to some modern research, you could also discuss from that massive gravity theories. Something nice to understand is e.g. why the massless limit of massive Fierz-Pauli theory does not give the results of linearized GR. This is called the vDVZ discontinuity (van Dam-Veltman-Zakharov). See e.g. the excellent notes

https://arxiv.org/abs/1105.3735

Just my 2 cents ;)

Depends on whether that professor has published on GW and about how much of the GR courses the uni offers you have followed.

All subjects are advanced at the cutting edge. And GW are no longer conjucture. A BSc thesis is just that. You need something you feel comfortable with as having as your thesis. Something you feel like you can work on for the set time and get some conclusion on before the deadline.

Gravitational waves are one of the simplerst solutions of Einstein's equation so that may be a good topic.

However, based on my current interests, I would also suggest thinking about the Reissner Nordstrom black hole. It's a charged black hole which has a lot of very interesting properties. Depending on the values of charge and mass it can have two event horizons, no event horizon, where r=0 is a naked singularity, or an extremal solution which is very mysterious. It has an event horizon (with a very interesting geometry) but is at zero temperature. As you may remember, the area of the event horizon is proportional to the BH entropy. So that means that extremal RN has a finite ground state entropy, which violates the third law of thermodynamics. There is a lot you could do here.

I'm not sure that massive gravity is a good idea since the theory has a lot of pathologies that need to be worked out.

Gold Member
Since its for a BS then how about how they traverse spacetime and how LIGO has successfully detected them. Other ideas could be how they are formed and their properties.

https://en.wikipedia.org/wiki/Gravitational_wave

As an aside:

Also one common issue is peoples conflation of gravity waves vs gravitational waves. They are separate phenomena. Here's a link for reference on gravity waves so you can see the difference

https://en.wikipedia.org/wiki/Gravity_wave
In my opinion a descriptive thesis that avoids math would be uninteresting. On the other hand, if you could say something about how GR gives rise to propoagating waves, as in https://en.wikipedia.org/wiki/Gravitational_wave#Mathematics
Are you comfortable with that level of math?
I'd think it's a suitable topic. I followed GR in the beginning of my third year, and this opens up a lot of interesting topics for a bachelor thesis.

In that direction it could be interesting to dive into linearized GR (= Fierz-Pauli theory), how gravitational waves emerge from such a linearization, and if you want to knot it to some modern research, you could also discuss from that massive gravity theories. Something nice to understand is e.g. why the massless limit of massive Fierz-Pauli theory does not give the results of linearized GR. This is called the vDVZ discontinuity (van Dam-Veltman-Zakharov). See e.g. the excellent notes

https://arxiv.org/abs/1105.3735

Just my 2 cents ;)
Depends on whether that professor has published on GW and about how much of the GR courses the uni offers you have followed.

All subjects are advanced at the cutting edge. And GW are no longer conjucture. A BSc thesis is just that. You need something you feel comfortable with as having as your thesis. Something you feel like you can work on for the set time and get some conclusion on before the deadline.
Gravitational waves are one of the simplerst solutions of Einstein's equation so that may be a good topic.

However, based on my current interests, I would also suggest thinking about the Reissner Nordstrom black hole. It's a charged black hole which has a lot of very interesting properties. Depending on the values of charge and mass it can have two event horizons, no event horizon, where r=0 is a naked singularity, or an extremal solution which is very mysterious. It has an event horizon (with a very interesting geometry) but is at zero temperature. As you may remember, the area of the event horizon is proportional to the BH entropy. So that means that extremal RN has a finite ground state entropy, which violates the third law of thermodynamics. There is a lot you could do here.

I'm not sure that massive gravity is a good idea since the theory has a lot of pathologies that need to be worked out.
Thank you for your answers. The thing is that I have not studied General Relativity yet, so I would have to study it on my own and write the thesis afterwards. All of that during only this summertime. Taking that into account, do you still think that I could manage to write on those topics?

Staff Emeritus