All Questions
Tagged with lagrangian-formalism string-theory
145 questions
2
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44
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SUSY QM as point-particle limit of Superstrings
There is a pretty clear resemblance between the Lagrangians for SUSY QM (1-dim susy sigma model) and various superstring theories (2-dim susy sigma models).
Again intuitively, one should expect the ...
- 538
1
vote
1
answer
81
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Einstein Frame from String Frame
Consider the following low-energy effective action in $D$ dimensions for the bosonic sector:
$$
I=\frac{1}{2\kappa_0^2}\int d^Dx\sqrt{-g}e^{-{2\Phi}}\left[R-2\Lambda+4g_{\mu\nu}\partial^\mu\Phi\...
3
votes
1
answer
136
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Schrödinger equation in string theory
D. Tong in his lecture note "String Theory" has mentioned on pages 11 and 12 on the contest of relativistic point particle that:
"We introduce a wavefunction $\Psi (X)$ which satisfies ...
- 834
8
votes
1
answer
410
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Non-perturbative Calculation of $\beta$ functions of tachyons in closed bosonic string theory
I am following the reference [1] https://inspirehep.net/literature/247397, which tells how to calculate beta functions using the weak field expansion for closed bosonic string theory.
Consider closed ...
- 161
1
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1
answer
113
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Witten's cubic open string field action is gauge invariant?
In the book "String theory and M-theory" by Becker-Becker-Schwarz on page 104 the author introduces the Witten's action of open string field theory as follows: $$S= \int \Big( A*Q_B A+\frac{...
- 834
0
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1
answer
100
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Has Carl Brans got the wrong Brans-Dicke parameter ($w=1$) for String Theory?
In his 2005 paper The roots of scalar-tensor theory: an approximate history Carl H.Brans claims his Brans-Dicke Theory whose field equations can be derived from the following action
accords with ...
- 6,073
2
votes
0
answers
37
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RNS string action in complex coordinates
The action for the Ramond-Neveu-Schwarz string in conformal gauge $h_{\alpha \beta}=\eta_{\alpha \beta}$ of the world-sheet is (for $\alpha '=1/2$ or $T=1/\pi$) $$S=-\frac{1}{2\pi}\int d^2 \sigma \Big(...
- 834
2
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0
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45
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Getting the Double Field Theory action from the projectors
I am mainly focusing on the following paper by Olaf Hohm and Barton Zwiebach: On the Riemann Tensor in Double Field Theory, so I'll give broad brushstrokes as to what my qualms are.
The DFT (Double ...
- 123
3
votes
1
answer
124
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Supercharge of supersymmetry transformations of the super-world-sheet coordinates
In the book "String theory and M-theory", the authors mentions on page 114 that "the generators of supersymmetry transformations of the super-world-sheet coordinates, called ...
- 834
2
votes
0
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55
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Pauli-Villars ghosts in the bosonic string theory and critical dimensions
I am a bit confused about the relation between Pauli-Villars ghosts and the need for Faddeev-Popov ghosts in the bosonic string when performing canonical quantisation.
The first encounter with ...
- 609
1
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0
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62
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Light-cone gauge
I'm trying to understand the existence of the light-cone gauge for the closed bosonic string in a more mathematical precise language.
Namely, when looking for critical points of Polyakov action, we ...
- 538
1
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0
answers
62
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Question on Ward Identities and on Noether's theorem
I am reading Polchinski's book on string theory (vol. 1), Chap. 2 subchapter "Ward identities and Noether's current".
At some point, in Eq. (2.3.12), the author claims that under spacetime ...
- 4,253
3
votes
2
answers
203
views
Periodicity of the dual scalar in $T$-duality
This question concerns the dual scalar (Lagrange multiplier) field $\lambda$, which appears in discussions of $T$-duality (e.g. in section 7.5.1 of David Tong's notes where it is called $\tilde\phi$).
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- 469
1
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0
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50
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On the Gauge-fixing for the case of the Polyakov string action
In the book "String theory and M-theory" by Becker-Becker-Schwarz, the author says that
"reparametrization invariance of the string sigma-model action $$S_{\sigma}=\frac{-T}{2}\int d^2 ...
- 834
3
votes
1
answer
113
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Where this definition $T_{\alpha\beta}=-\frac{2}{T}\frac{1}{\sqrt{-h}}\frac{\delta S}{\delta h^{\alpha \beta}}$ come from?
In the book "String theory and M-theory" by Becker, Becker and Schwarz, the author says that the Nambu-Goto action $$S_{NG}=-T\int d\sigma\, \tau \sqrt{(\dot{X}\cdot X')^2 -\dot{X}^2X'^2}$$ ...
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