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Light composite fermions from holography

Motivated by Beyond the Standard Model theories of composite fermions or top partners, we propose a holographic mechanism that generates light baryonic states in a strongly coupled gauge theory. The starting point are the fermionic fluctuations of massive probe branes embedded into AdS$_5 \times S^5$. We first consider the D3/probe D7-brane system. We derive in detail the fermionic fluctuation equations and show the supersymmetric degeneracy of the mesinos with the mesons. Here we view the fermionic mesinos as potential realizations of composite fermions or top partners. We then add higher dimension operators and study their impact on the mesino spectrum. In particular we show that the ground state mesino mass can be pushed to an arbitrarily light value by a suitable choice of the coupling of the higher dimension operator, $g$. No matter the value of $g$, the masses of higher excited states never fall below the mass of the ground state at $g=0$. We also present similar results for the supersymmetric D3/D3 and D3/D5 systems.