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N=2 Supersymmetric Gauge Theories with Nonpolynomial Interactions

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3.4. Chern-Simons Couplings 49<br />

To conclude this section, let us concentrate on the gauge field part of the model by<br />

freezing the scalars to constants (in particular Z = i and L = 0) and neglecting the<br />

fermions. Dropping the total derivative, the complete Lagrangian (3.61) reduces to<br />

L = − 1<br />

4 V µν Vµν − 1<br />

2E (Hµ + V µν Aν) 2 + 1<br />

2E (AµH µ ) 2 − 1<br />

4g2 F<br />

z<br />

µν Fµν , (3.64)<br />

where a kinetic term for Aµ originating from Lcc, eq. (1.48), has been added. Supersymmetry<br />

has now been broken explicitly of course, but the gauge invariances remain<br />

intact. After a rescaling Aµ → gzAµ, such that all fields have canonical dimension one 1 ,<br />

we can expand the Lagrangian in powers of the coupling constant gz, which gives up<br />

to first order<br />

L = − 1<br />

4 V µν Vµν − 1<br />

2 Hµ Hµ − 1<br />

4 F µν Fµν + gzAµV µν Hν + O(g 2 z) , (3.65)<br />

and we recognize the coupling of Aµ to the current J µ z from eq. (2.16).<br />

The Lagrangian (3.64) had previously been found outside the framework of supersymmetry<br />

in [24], and is actually but one example of a whole class of gauge theories known<br />

as Henneaux-Knaepen models, which we review in the last section of this chapter.<br />

3.4 Chern-Simons Couplings<br />

Let us now consider the more general solution (3.16) to the consistency conditions<br />

(C.1–4), containing an arbitrary holomorphic function g(Z). We note that in every<br />

coefficient it is accompanied by a factor ¯ Z. This may be removed by a field redefinition<br />

L = ˆ L + f(Z) + ¯ f( ¯ Z)<br />

<strong>with</strong> ∂f = g, for the transformation rules (2.54) give (dropping the hats)<br />

C = 1 <br />

¯Z<br />

L + h + ¯ ∂h<br />

h , D =<br />

− Z<br />

¯Z − Z , E = ¯ ∂¯ h<br />

¯Z − Z<br />

, (3.66)<br />

while the other coefficients are unchanged. Here h = Zg + f. The functions u and v in<br />

eqs. 25) and 26) do not vanish anymore, but one has<br />

L + ZC + ¯ Z ¯ C = −(h + ¯ h) , ZD + ¯ ZĒ = −∂h ,<br />

which however is compatible <strong>with</strong> condition (C.4). We now write the constraints as<br />

D (i<br />

α ¯ D j)<br />

L = 0<br />

˙α<br />

D (i D j) L = 2<br />

¯Z − Z<br />

D (i Z D j) L + ¯ D (i ¯ Z ¯ D j) L + 1<br />

2 L Di D j Z<br />

− i D i D j F + i ¯ D i ¯ D j ¯ F ,<br />

1 Recall that the coupling constant gz has mass dimension −1.<br />

(3.67)

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