Marco van den Beld-Serrano | Universität Regensburg (original) (raw)
Uploads
Papers by Marco van den Beld-Serrano
Annales Henri Poincaré, Apr 26, 2024
Given an extendible spacetime one may ask how much, if any, uniqueness can in general be expected... more Given an extendible spacetime one may ask how much, if any, uniqueness can in general be expected of the extension. Locally, this question was considered and comprehensively answered in a recent paper of Sbierski [22], where he obtains local uniqueness results for anchored spacetime extensions of similar character to earlier work for conformal boundaries by Chruściel [2]. Globally, it is known that non-uniqueness can arise from timelike geodesics behaving pathologically in the sense that there exist points along two distinct timelike geodesics which become arbitrarily close to each other interspersed with points which do not approach each other. We show that this is in some sense the only obstruction to uniqueness of maximal future boundaries: Working with extensions that are manifolds with boundary we prove that, under suitable assumptions on the regularity of the considered extensions and excluding the existence of such "intertwined timelike geodesics", extendible spacetimes admit a unique maximal future boundary extension. This is analogous to results of Chruściel for the conformal boundary.
The Journal of Physical Chemistry A, 2020
We present two methods for studying reactive collisions between two atomic or molecular species: ... more We present two methods for studying reactive collisions between two atomic or molecular species: a collinear merged-beam method, in which two gas pulses from a single supersonic beam source are coalesced, and an intrabeam-scattering technique, in which a single gas pulse is used. Both approaches, which rely on the laser cooling and deceleration of a laser-coolable species inside a Zeeman slower, can be used for a wide range of scattering studies. Possible experimental implementations of the proposed methods are outlined for autoionizing collisions between helium atoms in the metastable 2 3 S 1 state and a second, atomic or molecular species. Using numerical trajectory calculations, we provide estimates of the expected on-axis detection efficiency, collisionenergy range and collision-energy resolution of the approach. We have experimentally tested the feasibility of such an experiment by producing two gas pulses at very short time intervals, and the results of these measurements are detailed as well.
Annales Henri Poincaré, Apr 26, 2024
Given an extendible spacetime one may ask how much, if any, uniqueness can in general be expected... more Given an extendible spacetime one may ask how much, if any, uniqueness can in general be expected of the extension. Locally, this question was considered and comprehensively answered in a recent paper of Sbierski [22], where he obtains local uniqueness results for anchored spacetime extensions of similar character to earlier work for conformal boundaries by Chruściel [2]. Globally, it is known that non-uniqueness can arise from timelike geodesics behaving pathologically in the sense that there exist points along two distinct timelike geodesics which become arbitrarily close to each other interspersed with points which do not approach each other. We show that this is in some sense the only obstruction to uniqueness of maximal future boundaries: Working with extensions that are manifolds with boundary we prove that, under suitable assumptions on the regularity of the considered extensions and excluding the existence of such "intertwined timelike geodesics", extendible spacetimes admit a unique maximal future boundary extension. This is analogous to results of Chruściel for the conformal boundary.
The Journal of Physical Chemistry A, 2020
We present two methods for studying reactive collisions between two atomic or molecular species: ... more We present two methods for studying reactive collisions between two atomic or molecular species: a collinear merged-beam method, in which two gas pulses from a single supersonic beam source are coalesced, and an intrabeam-scattering technique, in which a single gas pulse is used. Both approaches, which rely on the laser cooling and deceleration of a laser-coolable species inside a Zeeman slower, can be used for a wide range of scattering studies. Possible experimental implementations of the proposed methods are outlined for autoionizing collisions between helium atoms in the metastable 2 3 S 1 state and a second, atomic or molecular species. Using numerical trajectory calculations, we provide estimates of the expected on-axis detection efficiency, collisionenergy range and collision-energy resolution of the approach. We have experimentally tested the feasibility of such an experiment by producing two gas pulses at very short time intervals, and the results of these measurements are detailed as well.