| 1. |
- Buarque Franzosi, Diogo, 1983, et al.
(författare)
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Anomalous dimensions of potential top-partners
- 2019
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Ingår i: SciPost Physics. - 2542-4653. ; 7:3
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Tidskriftsartikel (refereegranskat)abstract
- We discuss anomalous dimensions of top-partner candidates in theories of Partial Compositeness. First, we revisit, confirm and extend the computation by DeGrand and Shamir of anomalous dimensions of fermionic trilinears. We present general results applicable to all matter representations and to composite operators of any allowed spin. We then ask the question of whether it is reasonable to expect some models to have composite operators of sufficiently large anomalous dimension to serve as top-partners. While this question can be answered conclusively only by lattice gauge theory, within perturbation theory we find that such values could well occur for some specific models. In the Appendix we collect a number of practical group theory results for fourth-order invariants of general interest in gauge theories with many irreducible representations of fermions.
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| 2. |
- Closset, Cyril, et al.
(författare)
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Five-dimensional SCFTs and gauge theory phases : an M-theory/type IIA perspective
- 2019
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Ingår i: SciPost Physics. - 2542-4653. ; 6:5
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Tidskriftsartikel (refereegranskat)abstract
- We revisit the correspondence between Calabi-Yau (CY) threefold isolated singularities X and five-dimensional superconformal field theories (SCFTs), which arise at low energy in M-theory on the space-time transverse to X. Focussing on the case of toric CY singularities, we analyze the "gauge-theory phases" of the SCFT by exploiting fiberwise M-theory/type IIA duality. In this setup, the low-energy gauge group simply arises on stacks of coincident D6-branes wrapping 2-cycles in some ALE space of type AM−1 fibered over a real line, and the map between the K\"ahler parameters of X and the Coulomb branch parameters of the field theory (masses and VEVs) can be read off systematically. Different type IIA "reductions" give rise to different gauge theory phases, whose existence depends on the particular (partial) resolutions of the isolated singularity X. We also comment on the case of non-isolated toric singularities. Incidentally, we propose a slightly modified expression for the Coulomb-branch prepotential of 5d N=1 gauge theories.
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| 3. |
- de Juan, F., et al.
(författare)
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Conditions for fully gapped topological superconductivity in topological insulator nanowires
- 2019
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Ingår i: SciPost Physics. - : SciPost Foundation. - 2542-4653. ; 6:5
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Tidskriftsartikel (refereegranskat)abstract
- Among the different platforms to engineer Majorana fermions in one-dimensional topological superconductors, topological insulator nanowires remain a promising option. Threading an odd number of flux quanta through these wires induces an odd number of surface channels, which can then be gapped with proximity induced pairing. Because of the flux and depending on energetics, the phase of this surface pairing may or may not wind around the wire in the form of a vortex. Here we show that for wires with discrete rotational symmetry, this vortex is necessary to produce a fully gapped topological superconductor with localized Majorana end states. Without a vortex the proximitized wire remains gapless, and it is only if the symmetry is broken by disorder that a gap develops, which is much smaller than the one obtained with a vortex. These results are explained with the help of a continuum model and validated numerically with a tight binding model, and highlight the benefit of a vortex for reliable use of Majorana fermions in this platform. Copyright F. de Juan et al.
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| 4. |
- Herviou, Loic, et al.
(författare)
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Entanglement spectrum and symmetries in non-Hermitian fermionic non-interacting models
- 2019
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Ingår i: SciPost Physics. - : SciPost Foundation. - 2542-4653. ; 7:5
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Tidskriftsartikel (refereegranskat)abstract
- We study the properties of the entanglement spectrum in gapped non-interacting non-Hermitian systems, and its relation to the topological properties of the system Hamiltonian. Two different families of entanglement Hamiltonians can be defined in non-Hermitian systems, depending on whether we consider only right (or equivalently only left) eigenstates or a combination of both left and right eigenstates. We show that their entanglement spectra can still be computed efficiently, as in the Hermitian limit. We discuss how symmetries of the Hamiltonian map into symmetries of the entanglement spectrum depending on the choice of the many-body state. Through several examples in one and two dimensions, we show that the biorthogonal entanglement Hamiltonian directly inherits the topological properties of the Hamiltonian for line gapped phases, with characteristic singular and energy zero modes. The right (left) density matrix carries distinct information on the topological properties of the many-body right (left) eigenstates themselves. In purely point gapped phases, when the energy bands are not separable, the relation between the entanglement Hamiltonian and the system Hamiltonian breaks down.
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| 5. |
- Naseer, Usman
(författare)
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(1,0) gauge theories on the six-sphere
- 2019
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Ingår i: SciPost Physics. - : SciPost Foundation. - 2542-4653. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- We construct gauge theories with a vector-multiplet and hypermultiplets of (1,0) supersymmetry on the six-sphere. The gauge coupling on the sphere depends on the polar angle. This has a natural explanation in terms of the tensor branch of (1,0) theories on the six-sphere. For the vector-multiplet we give an off-shell formulation for all supersymmetries. For hypermultiplets we give an off-shell formulation for one supersymmetry. We show that the path integral for the vector-multiplet localizes to solutions of the Hermitian-Yang-Mills equation, which is a generalization of the (anti-)self duality condition to higher dimensions. For the hypermultiplet, the path integral localizes to configurations where the field strengths of two complex scalars are related by an almost complex structure.
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| 6. |
- Stålhammar, Marcus, et al.
(författare)
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Hyperbolic nodal band structures and knot invariants
- 2019
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Ingår i: SciPost Physics. - 2542-4653. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- We extend the list of known band structure topologies to include a large family of hyperbolic nodal links and knots, occurring both in conventional Hermitian systems where their stability relies on discrete symmetries, and in the dissipative non-Hermitian realm where the knotted nodal lines are generic and thus stable towards any small perturbation. We show that these nodal structures, taking the forms of Turk's head knots, appear in both continuum- and lattice models with relatively short-ranged hopping that is within experimental reach. To determine the topology of the nodal structures, we devise an efficient algorithm for computing the Alexander polynomial, linking numbers and higher order Milnor invariants based on an approximate and well controlled parameterisation of the knot.
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