2,847 reputation
939
bio website edwardfhughes.wordpress.com
location London, UK
age 24
visits member for 2 years, 10 months
seen 17 hours ago

I'm a PhD student at Queen Mary, University of London. I'm interested in modern approaches to scattering amplitudes, in particular twistor methods.


18h
comment Can you take the cutoff to infinity at a conformal fixed point?
Yes - I shall do over the weekend. Thanks for the bounty btw!
May
22
reviewed Approve What would be the rate of acceleration from gravity in a hollow sphere?
May
21
awarded  Custodian
May
12
revised Can you take the cutoff to infinity at a conformal fixed point?
added detail
May
12
revised Can you take the cutoff to infinity at a conformal fixed point?
Added details
May
12
asked Can you take the cutoff to infinity at a conformal fixed point?
May
6
comment Why do we need complex representations in Grand Unified Theories?
My point about the reality of the representation is this. If the representation is real then both left handed fermions and left-handed anti-fermions transform in the same representation $R$. Effective field theory then says that both left-handed fermions and left-handed anti-fermions should couple to the weak gauge field (you have to write down all couplings that are consistent with the symmetries of the system). But this means that your theory is non-chiral, which is against experimental evidence!
May
6
comment Why do we need complex representations in Grand Unified Theories?
@JakobH - I'm afraid I still disagree with you. Charge conjugation to me means reversing the charge but keeping the same helicity. This is borne out by the Wikipedia page I linked. You ask "what's the problem with our theory being non-chiral"? The answer is - experiment! All the experimental evidence shows that we must have a chiral theory. Unless you want to invent new particles that haven't been observed (which is fair enough) you must have a chiral theory.
May
4
comment Why do we need complex representations in Grand Unified Theories?
To the downvoters - please do have a look at my updated answer. I've removed the vague (and probably wrong) statement about preserving the reality of the Lagrangian! I've also clarified my argument based on representation theory. If you've got any more concerns, do let me know!
May
4
comment Why do we need complex representations in Grand Unified Theories?
@JakobH: apologies for the delay - I've been away. I've now updated my answer, trying to address your concerns. Thanks very much for your questions, they've really helped me deepen my thoughts on the subject! I think the key point is that charge conjugation preserves the chirality of the particle, so then CPT symmetry predicts a theory with both left and right handed fermions coupling to the weak force. But you are absolutely right, if we hypothesize 3 new generations of mirror matter then we can get around the problem! Whether or not you find this appealing is a matter of taste :).
May
4
revised Why do we need complex representations in Grand Unified Theories?
Added details
May
4
revised Why do we need complex representations in Grand Unified Theories?
removed vague statement, added references
May
4
comment Extended object passing near an event horizon
zwol: Brilliant - glad to be of help! @Rick - it's not really possible that the event horizon gets perturbed in the way you describe. That's because the event horizon is effectively just a function of the mass inside the black hole. Either $B$ crosses the horizon and the black hole gets bigger, or $B$ doesn't in which case it can escape again!
May
2
awarded  Popular Question
Apr
30
comment Why do we need complex representations in Grand Unified Theories?
I can't think of any, unless you want to define a completely new way of understanding particle physics which doesn't use gauge symmetry! As far as I'm aware you can use octonionic representations of $E_8$ to get chiral unified theories. Effectively the octonions are a generalization of the complex numbers. So although $E_8$ doesn't admit complex representations, it can still give you chiral theories via octonions. I'm not an expert on this model, however!
Apr
30
answered Why do we need complex representations in Grand Unified Theories?
Apr
30
reviewed Approve Is there a huge difference between centrifugal and centripetal forces?
Apr
27
comment Extended object passing near an event horizon
Yes - I would agree with that.
Apr
27
answered Extended object passing near an event horizon
Apr
27
comment Two and three point function of primary fields of arbitrary fields
Sorry - the $2$ was a typo! Do let me know if you have any questions about the paper and I'll try to help you out.