6,748 reputation
11033
bio website pantheon.yale.edu/~pwm22
location New Haven, CT
age 58
visits member for 4 years, 7 months
seen Jun 19 at 2:20

I'm slowly understanding quantum field theory. I believe I understand non-interacting quantum fields pretty well, I would say as a formalism for real signal analysis, and their relationship to classical random fields, but the mathematics and understanding of interacting quantum fields is harder.

As a manifesto for PhysicsSE, I would say that research in Physics is a cooperative endeavour, in which productive failures are sometimes better for us than apparent successes. Sometimes seeing what is productive takes the ingenuity of many people and many years.


Feb
20
reviewed Approve Do electrons have shape?
Feb
20
comment What is the temperature of an LHC Bunch?
@DarioP thanks. So I find somewhere that the energy spread is about $\mbox{1e-4}*\mbox{7TeV}=\mbox{700MeV}=m_p\gamma (\Delta v)^2$, where $\gamma\approx \frac{\mbox{7TeV}}{\mbox{1GeV}}=7000$, so $m_p(\Delta v)^2\approx 0.1MeV$ and $T\approx \mbox{(1e5eV)}*\mbox{(1.6e-19joule/eV)}/\mbox{(1.38e-23joule/K)}$ $\approx \mbox{1e9K}$. Within a couple of orders of magnitude of the transverse temperature, slightly smaller than the transverse temperature at the IP where there's greater transverse pressure but slightly larger elsewhere.
Feb
16
comment What is the temperature of an LHC Bunch?
I have from the Moehl lecture, $k_BT\approx m_p(\beta\gamma c)^2\epsilon/\beta_x\approx m_pc^2\beta\gamma\epsilon_n/\beta_x$, where $m_pc^2\beta\gamma$ is very nearly the beam energy per proton, so $T\approx\mbox{(7e12eV)}*\mbox{(1.6e-19joule/eV)}*\mbox{(2.5e-6m)}/\mbox{(0.44m)‌​}/\mbox{(1.38e-23joule/K)}$ $=\mbox{4.6e11K}$, taking numbers from rdemaria.web.cern.ch/rdemaria/www/hllhc11. I wasn't expecting something quite that high!?
Feb
14
asked What is the temperature of an LHC Bunch?
Jan
25
awarded  Yearling
Dec
21
awarded  Popular Question
Dec
7
comment Renormalization in non-relativistic quantum mechanics
Similarly useful: Regularization, renormalization, and dimensional analysis: Dimensional regularization meets freshman E&M Fredrick Olness and Randall Scalise Citation: American Journal of Physics 79, 306 (2011); doi: 10.1119/1.3535586 View online: dx.doi.org/10.1119/1.3535586
Nov
29
revised Does the lagrangian contain all the information about the representations of the fields in QFT?
Added response to comment from Question author.
Nov
28
comment Does the lagrangian contain all the information about the representations of the fields in QFT?
@glance Right, and apologies. Read the Question carefully. I take it that there are two aspects to the question: the local and the global. See my Edit, to appear momentarily, I hope.
Nov
27
answered Does the lagrangian contain all the information about the representations of the fields in QFT?
Oct
6
awarded  Popular Question
Sep
30
awarded  Explainer
Jul
2
awarded  Inquisitive
Jul
2
awarded  Curious
Apr
3
awarded  Nice Question
Feb
18
awarded  Custodian
Feb
18
reviewed Approve How does one measure the frequency of a laser?
Jan
25
awarded  Yearling
Dec
20
awarded  Enlightened
Dec
20
awarded  Nice Answer