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seen Jun 26 at 12:15

Dec
10
comment How to understand exciton?
@KabaT: The hole is basically an atom that is missing an electron. But that picture is not quite accurate, since the atom is fixed in the lattice, but the hole moves around. A better picture would be to imagine a hole in the electron cloud that moves around as if it were a particle. Or think of it as an air bubble: When you excite an electon above the gap, you have a "droplet of water" in the upper band, and a "bubble of air" of same volume in the lower band. It is an absense of water, but behaves like a droplet...
Dec
8
awarded  Custodian
Dec
8
reviewed No Action Needed when water falls to the ground and forms a puddle, where does most of the energy go?
Dec
8
answered How to understand exciton?
Dec
8
answered What is anti-time?
Dec
8
comment $D$ and $H$ in macroscopic Maxwell's equation: auxiliary or constitutive?
@HuiZhang right, thanks, fixed it.
Dec
8
revised $D$ and $H$ in macroscopic Maxwell's equation: auxiliary or constitutive?
fixed typo
Dec
8
answered $D$ and $H$ in macroscopic Maxwell's equation: auxiliary or constitutive?
Dec
6
comment Free HEP dataset for teaching and demo purposes?
The Masterclasses are cool, we also offer ATLAS/LHC Masterclasses at our institute. However, its not quite what I'm looking for. The data is highly processed, and it's targeted to high school students as you say. I'm looking for something you could give bachelor/master students, or something you could use to make example plots for a book.
Dec
6
asked Textbook about the handiwork of a HEP analysis?
Dec
6
asked Free HEP dataset for teaching and demo purposes?
Nov
27
comment Photons from stars--how do they fill in such large angular distances?
A corollary question to this is: Are the photons we receive from stars localized to classical trajectories, or are they spread out? If so, how much? Does the photon's wavefunction look more like the tip of a ray, or more like an expanding half-sphere?
Nov
26
comment What exactly means “is a singlet under $SU(N)$”
In addition to the linked thread: A SU(2) doublet is a pair of states (particles) which can be rotated into each other by SU(2) (gauge) transformations. You have weak isospin ($T_3$) up and down, but you are free to e.g. replace up <-> down everywhere without changing the physics. A singlet has no SU(2) "charge" and it not affected by the transformation. In the SM, left-handed leptons are SU(2) doublets $(e, \nu)_L$, $T_3 = \pm 1/2$, and right-handed ones SU(2) singlets $e_R$, $T_3$ = 0. In the same way, you have color triplets (quarks), singlets (leptons), and octets (gluons) under SU(3).
Nov
22
accepted Why does the $\tilde\chi^0_2 \,\tilde\chi^\pm_1$ cross section increase in the focus point region?
Nov
22
comment Running chargino/neutralino masses in MSSM
@innisfree I'm aware that pole masses are scale independent (what one might call the "physical" mass). What I'm interested in is the running mass. Probe a particle in low- and high-energy interactions, and you will see a different apparent mass due to screening effects/quantum corrections, right? $m(\tilde g)(Q) = M_3$, since gluinos don't mix. I'm interested in $m(\tilde\chi^\pm_i)(Q)$, if that makes sense. I am not really interested in the effect of the renormalization scale choice (what one might sloppily call cutoff scale) on the pole masses, which is more of a computational effect.
Nov
22
asked Running chargino/neutralino masses in MSSM
Nov
21
comment Infinitesimal Lorentz transformation is antisymmetric
@Qmechanic: Why the homework tag? "[...] any question where it is preferable to guide the asker to the answer rather than giving it away outright." - If it's not actual homework, shouldn't the OP decide what kind of answer he'd prefer? If I asked the question and needed the answer for actual work, I'd be very unhappy if given a pedagogical answer.
Oct
6
awarded  Critic
Oct
2
asked Why does the $\tilde\chi^0_2 \,\tilde\chi^\pm_1$ cross section increase in the focus point region?
Aug
4
awarded  Good Question