1,133 research outputs found
Controlling the net charge on a nanoparticle optically levitated in vacuum
Optically levitated nanoparticles in vacuum are a promising model system to
test physics beyond our current understanding of quantum mechanics. Such
experimental tests require extreme control over the dephasing of the levitated
particle's motion. If the nanoparticle carries a finite net charge, it
experiences a random Coulomb force due to fluctuating electric fields. This
dephasing mechanism can be fully excluded by discharging the levitated
particle. Here, we present a simple and reliable technique to control the
charge on an optically levitated nanoparticle in vacuum. Our method is based on
the generation of charges in an electric discharge and does not require
additional optics or mechanics close to the optical trap
Stable moduli spaces of hermitian forms
We prove that Grothendieck-Witt spaces of Poincar\'e categories are, in many
cases, group completions of certain moduli spaces of hermitian forms. This, in
particular, identifies Karoubi's classical hermitian and quadratic K-groups
with the genuine Grothendieck-Witt groups from our joint work with Calm\`es,
Dotto, Harpaz, Land, Moi, Nardin and Nikolaus, and thereby completes our
solution of several conjectures in hermitian K-theory. The method of proof is
abstracted from work of Galatius and Randal-Williams on cobordism categories of
manifolds using the identification of the Grothendieck-Witt space of a
Poincar\'e category as the homotopy type of the associated cobordism category.Comment: 94 pages, v2: New appendix by Y.Harpaz that gives a simplified proof
of the main result in a special case, furthermore added Section 8.4 about
real algebraic K-spectra and made miscellaneous minor improvement
Multiplicative parametrized homotopy theory via symmetric spectra in retractive spaces
In order to treat multiplicative phenomena in twisted (co)homology, we introduce a new point-set-level framework for parametrized homotopy theory. We provide a convolution smash product that descends to the corresponding ∞-categorical product and allows for convenient constructions of commutative parametrized ring spectra. As an immediate application, we compare various models for generalized Thom spectra. In a companion paper, this approach is used to compare homotopical and operator algebraic models for twisted K-theory.publishedVersio
- …