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I just finished my freshman year as an undergraduate, but I'll tell you what I've learned. So I don't know if it's primarily due to the Higgs, but according to someone who almost has a PhD, SUSY has almost entirely been ruled out. Only "weird" SUSY theories are still acceptable. I watched a movie titled "Particle Fever" and according to the movie, the mass ...


2

It's a bit strange because the OP basically repeats the same statement twice. First, he says that he understands it and second, he says that he doesn't. But let's try to avoid these detailed surprising aspects of the question and try to explain what's going on, anyway or again. Type I/II strings have spacetime supercharges $Q_a$ that are constructed purely ...


1

They're not different at all! Seiberg has used the term electric-magnetic duality in the title of his famous paper, too. His duality is an electric-magnetic duality because the duality relates two descriptions and objects that are electrically charged under the gauge group on one side (e.g. quarks and gluons) are mapped to solitons (forms of magnetic ...


1

Your conclusion is true only for $N=1$ supersymmetry. If I have extended supersymmetry, then I can start from the graviton state and end up in a scalar state. What you are saying is true. If I have D-branes, I need to consider projections of all fields into normal and tangent directions onto the D-brane. The world-volume theory of the D-brane will contain ...


5

$t=0$ is completely consistent. It is simply too boring since it implies that in any unitary theory, $Q_\alpha |\psi\rangle = 0$ for any state $|\psi\rangle$. This is because in this case, we have $$ 0 = \langle\psi|\{ Q_\alpha , Q^\dagger_\alpha \} | \psi \rangle = \| Q^\dagger_\alpha |\psi\rangle \|^2 + \| Q_\alpha |\psi\rangle \|^2 $$ Positivity of ...


2

Yes, there is systematic way called the Noether procedure. Simply you write down all possible 2-derivative fermionic terms with arbitrary coefficients and vary the action using the SUSY transformation rules. Then, you fix the coefficients to obtain the invariance up to a total derivative. When you have 4-derivatives, there are two cases: a. Off-Shell ...


0

The idea behind this is not only drawing pretty interesecting lines; but to have a larger symmetry which includes all of the standard model (SM). To each simple group is attached a coupling 'constant': in the SM we have three of these because $G_{SM} = SU(3)_C \times SU(2)_L \times U(1)_Y$. The values of these coupling 'constants' vary with energy and this ...


1

The reason is clearly given in the famous paper "Vacuum configurations for superstrings" - http://www.sciencedirect.com/science/article/pii/0550321385906029 -. Here, I am just copying the introduction of that paper. I cannot tell the reason why with better words. Recently, the discovery [6] of anomaly cancellation in a modified version of d = 10 ...


0

If the vacuum of the theory is supersymmetric - i.e. SUSY is not broken - then it is annihilated by the SUSY generators. On the other hand, using the SUSY algebra one can show that the hamiltonian can be written in terms of the SUSY generators. This implies that the vacuum $|0\rangle$ is supersymmetric if and only if $\langle 0|H|0\rangle=0$, i.e. the vev ...


3

Let me first describe the basic idea without even mentioning supergravity. Consider some classical field theory of two fields $\phi$ and $\sigma$, with an action $S[\phi,\sigma]$. Suppose this theory has a continuous symmetry (with parameter $\epsilon$): $$S[\phi,\sigma]=S[\phi+\delta_\epsilon\phi,\sigma+\delta_\epsilon\sigma].$$ Say I find some particular ...



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