- #1

Al.Rivero@gmail.com

## Main Question or Discussion Point

I was wondering, OK it is a gedakenexperiment because it is beyond

observation, but... how is space-time supersymmetry (no worldsheet

susy) supossed to appear from the point of view of states of the

fundamental string? Do we observe entities with spin 0 and spin 1/2

having the same mass? And what happens for highly excited levels of the

string? If they mimic the QCD string, these excited levels have higher

spin. Do we have multiplets for, say, Spin 10 and spin 10 +- 1/2 ? Do

all these particles follow regge trajectories?

[Moderator's note: Yes, Alejandro, spacetime supersymmetry also has an

action on the worldsheet. Its existence is manifest in the Green-Schwarz

formalism - see chapter 5 of Green-Schwarz-Witten - while its existence

depends on seemingly miraculous identities such as Jacobi's obscure

formula - see chapter 4 of Green-Schwarz Witten. You can also see the

beginning of 2nd volume of Joe Polchinski's textbook, or many other

sources. Yes, spinning modes of the string with an arbitrarily high

spin have their superpartners whose spin differs by +-1/2 - or up to

+-2 in the case of maximal supersymmetry. Such superpartners lie

on the same Regge trajectory moved by +-1/2 or +-2 in the J direction.

Only one of these trajectories is really "leading" - one with maximal

J. Best wishes, LM]

observation, but... how is space-time supersymmetry (no worldsheet

susy) supossed to appear from the point of view of states of the

fundamental string? Do we observe entities with spin 0 and spin 1/2

having the same mass? And what happens for highly excited levels of the

string? If they mimic the QCD string, these excited levels have higher

spin. Do we have multiplets for, say, Spin 10 and spin 10 +- 1/2 ? Do

all these particles follow regge trajectories?

[Moderator's note: Yes, Alejandro, spacetime supersymmetry also has an

action on the worldsheet. Its existence is manifest in the Green-Schwarz

formalism - see chapter 5 of Green-Schwarz-Witten - while its existence

depends on seemingly miraculous identities such as Jacobi's obscure

formula - see chapter 4 of Green-Schwarz Witten. You can also see the

beginning of 2nd volume of Joe Polchinski's textbook, or many other

sources. Yes, spinning modes of the string with an arbitrarily high

spin have their superpartners whose spin differs by +-1/2 - or up to

+-2 in the case of maximal supersymmetry. Such superpartners lie

on the same Regge trajectory moved by +-1/2 or +-2 in the J direction.

Only one of these trajectories is really "leading" - one with maximal

J. Best wishes, LM]