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Register a new userOn Isometry Anomalies in Minimal N=(0,1) and N=(0,2) Sigma Models
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The two-dimensional minimal supersymmetric sigma models with homogeneous target spaces $G/H$ and chiral fermions of the same chirality are revisited. We demonstrate that the Moore-Nelson consistency condition revealing a global anomaly in CP(N-1) (with N>2 and ${mathcal N}=(0,2)$ supersymmetry) due to a nontrivial first Pontryagin class is in one-to-one correspondence with the local anomalies of isometries in these models. These latter anomalies are generated by fermion loop diagrams which we explicitly calculate. In the case of O}(N) sigma models the first Pontryagin class vanishes, so there is no global obstruction for the minimal ${mathcal N}=(0,1)$ supersymmetrization of these models. We show that at the local level isometries in these models are anomaly free. Thus, there are no obstructions to quantizing the minimal ${mathcal N}=(0,1)$ models with the $S^{N-1}= SO(N)/SO(N-1)$ target space. This also includes CP(1) (equivalent to $S^{2}$) which is an exceptional case from the CP(N-1) series. We also discuss a relation between the geometric and gauged formulations of the CP}(N-1) models.
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We construct connected (0,2) sigma models starting from n copies of (2,2) CP(N-1) models. General aspects of models of this type (known as T+O deformations) had been previously studied in the context of heterotic string theories. Our construction presents a natural generalization of the nonminimally deformed (2,2) model with an extra (0,2) fermion superfield on tangent bundle T CP(N-1) x C^1. We had thoroughly analyzed the latter model previously, found the exact beta function and a spontaneous breaking of supersymmetry. In contrast, in certain connected sigma models the spontaneous breaking of supersymmetry disappears. We study the connected sigma models in the large-N limit finding supersymmetric vacua and determining the particle spectrum. While the Witten index vanishes in all the models under consideration, in these special cases of connected models one can use a permutation symmetry to define a modification of the Witten index which does not vanish. This eliminates the spontaneous breaking of supersymmetry. We then examine the exact beta functions of our connected (0,2) sigma models.
We study chiral anomalies in $mathcal N=(0, 1)$ and $(0, 2)$ two-dimensional minimal sigma models defined on generic homogeneous spaces $G/H$. Such minimal theories contain only (left) chiral fermions and in certain cases are inconsistent because of incurable anomalies. We explicitly calculate the anomalous fermionic effective action and show how to remedy it by adding a series of local counter-terms. In this procedure, we derive a local anomaly matching condition, which is demonstrated to be equivalent to the well-known global topological constraint on $p_1(G/H)$. More importantly, we show that these local counter-terms further modify and constrain curable chiral models, some of which, for example, flow to nontrivial infrared superconformal fixed point. Finally, we also observe an interesting relation between $mathcal N=(0, 1)$ and $(0, 2)$ two-dimensional minimal sigma models and supersymmetric gauge theories. This paper generalizes and extends the results of our previous publication arXiv:1510.04324.
We holomorphically embed nonlinear sigma models (NLSMs) on $SO(2N)/U(N)$ and $Sp(N)/U(N)$ in the hyper-K{a}hler (HK) NLSM on the cotangent bundle of the Grassmann manifold $T^ast G_{2N,N}$, which is defined by $G_{N+M,M}=frac{SU(N+M)}{SU(N)times SU(M)times U(1)}$, in the ${mathcal{N}}=1$ superspace formalism and construct three-pronged junctions of the mass-deformed NLSMs (mNLSMs) in the moduli matrix formalism (MMF) by using a recently proposed method.
We study vacua, walls and three-pronged junctions of mass-deformed nonlinear sigma models on $SO(2N)/U(N)$ and $Sp(N)/U(N)$ for generic $N$. We review and discuss the on-shell component Lagrangians of the ${mathcal{N}}=2$ nonlinear sigma model on the Grassmann manifold, which are obtained in the ${mathcal{N}}=1$ superspace formalism and in the harmonic superspace formalism. We also show that the K{a}hler potential of the ${mathcal{N}}=2$ nonlinear sigma model on the complex projective space, which is obtained in the projective superspace formalism, is equivalent to the K{a}hler potential of the ${mathcal{N}}=2$ nonlinear sigma model with the Fayet-Iliopoulos parameters $c^a=(0,0,c=1)$ on the complex projective space, which is obtained in the ${mathcal{N}}=1$ superspace formalism.
We study vacua and walls of mass-deformed Kahler nonlinear sigma models on $Sp(N)/U(N)$. We identify elementary walls with the simple roots of $USp(2N)$ and discuss compressed walls, penetrable walls and multiwalls by using the moduli matrix formalism.
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