| 1. |
- Brivio, Ilaria, et al.
(författare)
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To profile or to marginalize : A SMEFT case study
- 2024
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Ingår i: SciPost Physics. - : Stichting SciPost. - 2542-4653. ; 16:1
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Tidskriftsartikel (refereegranskat)abstract
- Global SMEFT analyses have become a key interpretation framework for LHC physics, quantifying how well a large set of kinematic measurements agrees with the Standard Model. This agreement is encoded in measured Wilson coefficients and their uncertainties. A technical challenge of global analyses are correlations. We compare, for the first time, results from a profile likelihood and a Bayesian marginalization for a given data set with a comprehensive uncertainty treatment. Using the validated Bayesian framework we analyse a series of new kinematic measurements. For the updated dataset we find and explain differences between the marginalization and profile likelihood treatments.
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| 2. |
- Delcamp, Clement, et al.
(författare)
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Higher categorical symmetries and gauging in two-dimensional spin systems
- 2024
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Ingår i: SciPost Physics. - : SciPost Foundation. - 2542-4653. ; 16:4
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Tidskriftsartikel (refereegranskat)abstract
- We present a framework to systematically investigate higher categorical symmetries in two-dimensional spin systems. Though exotic, such generalised symmetries have been shown to naturally arise as dual symmetries upon gauging invertible symmetries. Our framework relies on an approach to dualities whereby dual quantum lattice models only differ in a choice of module 2-category over some input fusion 2-category. Given an arbitrary two-dimensional spin system with an ordinary symmetry, we explain how to perform the (twisted) gauging of any of its sub-symmetries. We then demonstrate that the resulting model has a symmetry structure encoded into the Morita dual of the input fusion 2-category with respect to the corresponding module 2-category. We exemplify this approach by specialising to certain finite group generalisations of the transversefield Ising model, for which we explicitly define lattice symmetry operators organised into fusion 2-categories of higher representations of higher groups.
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| 3. |
- Hartong, Jelle, et al.
(författare)
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A coupling prescription for post-Newtonian corrections in quantum mechanics
- 2024
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Ingår i: SciPost Physics. - : Stichting SciPost. - 2542-4653. ; 16:3
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Tidskriftsartikel (refereegranskat)abstract
- The interplay between quantum theory and general relativity remains one of the main challenges of modern physics. A renewed interest in the low -energy limit is driven by the prospect of new experiments that could probe this interface. Here we develop a covariant framework for expressing post -Newtonian corrections to Schr & ouml;dinger's equation on arbitrary gravitational backgrounds based on a 1/c2 expansion of Lorentzian geometry, where c is the speed of light. Our framework provides a generic coupling prescription of quantum systems to gravity that is valid in the intermediate regime between Newtonian gravity and General Relativity, and that retains the focus on geometry. At each order in 1/c2 this produces a nonrelativistic geometry to which quantum systems at that order couple. By considering the gauge symmetries of both the nonrelativistic geometries and the 1/c2 expansion of the complex Klein-Gordon field, we devise a prescription that allows us to derive the Schr & ouml;dinger equation and its post -Newtonian corrections on a gravitational background order -by -order in 1/c2. We also demonstrate that these results can be obtained from a 1/c2 expansion of the complex Klein-Gordon Lagrangian. We illustrate our methods by performing the 1/c2 expansion of the Kerr metric up to O(c-2), which leads to a special case of the Hartle-Thorne metric. The associated Schr & ouml;dinger equation captures novel and potentially measurable effects.
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| 4. |
- Kochergin, Daniil, et al.
(författare)
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Robust extended states in Anderson model on partially disordered random regular graphs
- 2024
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Ingår i: SciPost Physics. - : SCIPOST FOUNDATION. - 2542-4653. ; 16:4
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Tidskriftsartikel (refereegranskat)abstract
- In this work we analytically explain the origin of the mobility edge in the partially disordered random regular graphs of degree d, i.e., with a fraction beta of the sites being disordered, while the rest remain clean. It is shown that the mobility edge in the spectrum survives in a certain range of parameters (d, beta) at infinitely large uniformly distributed disorder. The critical curve separating extended and localized states is derived analytically and confirmed numerically. The duality in the localization properties between the sparse and extremely dense RRG has been found and understood.
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| 5. |
- Kutlin, Anton, et al.
(författare)
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Anatomy of the eigenstates distribution : A quest for a genuine multifractality
- 2024
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Ingår i: SciPost Physics. - : Stichting SciPost. - 2542-4653. ; 16:1
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by a series of recent works, an interest in multifractal phases has risen as they are believed to be present in the Many-Body Localized (MBL) phase and are of high demand in quantum annealing and machine learning. Inspired by the success of the Rosenzweig-Porter (RP) model with Gaussian-distributed hopping elements, several RP -like ensembles with the fat-tailed distributed hopping terms have been proposed, with claims that they host the desired multifractal phase. In the present work, we develop a general (graphical) approach allowing a self-consistent analytical calculation of frac-tal dimensions for a generic RP model and investigate what features of the RP Hamil-tonians can be responsible for the multifractal phase emergence. We conclude that the only feature contributing to a genuine multifractality is the on-site energies' distribution, meaning that no random matrix model with a statistically homogeneous distribution of diagonal disorder and uncorrelated off-diagonal terms can host a multifractal phase.
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| 6. |
- Schobert, Arne, et al.
(författare)
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Ab initio electron-lattice downfolding : Potential energy landscapes, anharmonicity, and molecular dynamics in charge density wave materials
- 2024
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Ingår i: SciPost Physics. - 2542-4653. ; 16:2
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Tidskriftsartikel (refereegranskat)abstract
- The interplay of electronic and nuclear degrees of freedom presents an outstanding problem in condensed matter physics and chemistry. Computational challenges arise especially for large systems, long time scales, in nonequilibrium, or in systems with strong correlations. In this work, we show how downfolding approaches facilitate complexity reduction on the electronic side and thereby boost the simulation of electronic properties and nuclear motion—in particular molecular dynamics (MD) simulations. Three different downfolding strategies based on constraining, unscreening, and combinations thereof are benchmarked against full density functional calculations for selected charge density wave (CDW) systems, namely 1H-TaS2, 1T-TiSe2, 1H-NbS2, and a one-dimensional carbon chain. We find that the downfolded models can reproduce potential energy surfaces on supercells accurately and facilitate computational speedup in MD simulations by about five orders of magnitude in comparison to purely ab initio calculations. For monolayer 1H-TaS2 we report classical and path integral replica exchange MD simulations, revealing the impact of thermal and quantum fluctuations on the CDW transition.
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| 7. |
- Seifert, Urban F. P., et al.
(författare)
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Wegner's Ising gauge spins versus Kitaev's Majorana partons : Mapping and application to anisotropic confinement in spin-orbital liquids
- 2024
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Ingår i: SciPost Physics. - 2542-4653. ; 16:6
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Tidskriftsartikel (refereegranskat)abstract
- Emergent gauge theories take a prominent role in the description of quantum matter, supporting deconfined phases with topological order and fractionalized excitations. A common construction of Z2 lattice gauge theories, first introduced by Wegner, involves Ising gauge spins placed on links and subject to a discrete Z2 Gauss law constraint. As shown by Kitaev, Z2 lattice gauge theories also emerge in the exact solution of certain spin systems with bond-dependent interactions. In this context, the Z2 gauge field is constructed from Majorana fermions, with gauge constraints given by the parity of Majorana fermions on each site. In this work, we provide an explicit Jordan-Wigner transformation that maps between these two formulations on the square lattice, where the Kitaev-type gauge theory emerges as the exact solution of a spin-orbital (Kugel-Khomskii) Hamiltonian. We then apply our mapping to study local perturbations to the spin-orbital Hamiltonian, which correspond to anisotropic interactions between electric-field variables in the Z2 gauge theory. These are shown to induce anisotropic confinement that is characterized by emergence of weakly-coupled one-dimensional spin chains. We study the nature of these phases and corresponding confinement transitions in both absence and presence of itinerant fermionic matter degrees of freedom. Finally, we discuss how our mapping can be applied to the Kitaev spin-1/2 model on the honeycomb lattice.
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| 8. |
- Seifert, Urban F.P., et al.
(författare)
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Wegner’s Ising gauge spins versus Kitaev’s Majorana partons : Mapping and application to anisotropic confinement in spin-orbital liquids
- 2024
-
Ingår i: SciPost Physics. - : SciPost Foundation. - 2542-4653. ; 16:6
-
Tidskriftsartikel (refereegranskat)abstract
- Emergent gauge theories take a prominent role in the description of quantum matter, supporting deconfined phases with topological order and fractionalized excitations. A common construction of Z2 lattice gauge theories, first introduced by Wegner, involves Ising gauge spins placed on links and subject to a discrete Z2 Gauss law constraint. As shown by Kitaev, Z2 lattice gauge theories also emerge in the exact solution of certain spin systems with bond-dependent interactions. In this context, the Z2 gauge field is constructed from Majorana fermions, with gauge constraints given by the parity of Majorana fermions on each site. In this work, we provide an explicit Jordan-Wigner transformation that maps between these two formulations on the square lattice, where the Kitaev-type gauge theory emerges as the exact solution of a spin-orbital (Kugel-Khomskii) Hamiltonian. We then apply our mapping to study local perturbations to the spin-orbital Hamiltonian, which correspond to anisotropic interactions between electric-field variables in the Z2 gauge theory. These are shown to induce anisotropic confinement that is characterized by emergence of weakly-coupled one-dimensional spin chains. We study the nature of these phases and corresponding confinement transitions in both absence and presence of itinerant fermionic matter degrees of freedom. Finally, we discuss how our mapping can be applied to the Kitaev spin-1/2 model on the honeycomb lattice.
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