arXiv subjects

Tristan Daus

Publications and source records attributed to Tristan Daus.

3 recordsLinked to original sources

arXiv2025

Cosmic Large-Scale Structure Formation from Newtonian Particle Dynamics

We present results for the cosmic non-linear density-fluctuation power spectrum based on the analytical formalism developed in [1] which allows us to study cosmic structure formation based on Newtonian particle dynamics in phase-space. This framework provides a field-theory approach to a perturbative solution of the BBGKY-hierarchy where the resulting loop-expansion of the theory introduces a natural truncation criterion. We show that we are able to reproduce structure growth on large scales $k \leq 0.2 \mathrm{h}\,\mathrm{Mpc}^{-1}$ to very high precision while on small and intermediate scales we find deviations of the order of $10\%$ from current numerical simulations. The results strongly suggest that a significant improvement may be achieved by restructuring the perturbation theory.

astro-ph.CO↗

arXiv2024

Field Theory Approach to Classical $N$-Particle Systems In and Out of Equilibrium

We present an approach to solving the evolution of a classical $N$-particle ensemble based on the path integral approach to classical mechanics. This formulation provides a perturbative solution to the Liouville equation in terms of a propagator which can be expanded in a Dyson series. We show that this perturbative expansion exactly corresponds to an iterative solution of the BBGKY-hierarchy in orders of the interaction potential. Using the path integral formulation, we perform a Hubbard-Stratonovich transformation (HST) to obtain an effective field theoretic description in terms of macroscopic fields, which contains the full microscopic dynamics of the system in its vertices. Naturally, the HST leads to a new perturbative expansion scheme which contains an infinite order of microscopic interactions already at the lowest order of the perturbative expansion. Our approach can be applied to in and out of equilibrium systems with arbitrary interaction potentials and initial conditions. We show how (unequal-time) cumulants of the Klimontovich phase space densities can be computed within this framework and derive results for density and momentum correlations for a spatially homogeneous system. Under the explicit assumptions for the interaction potential and initial conditions, we show that well-known results related to plasma oscillations and the Jeans instability criterion for gravitational collapse can be recovered in the lowest order perturbative expansion and that both are the effect of the same collective behaviour of the many-body system.

cond-mat.stat-mech↗

arXiv2020

Towards a Swampland Global Symmetry Conjecture using Weak Gravity

It is widely believed and in part established that exact global symmetries are inconsistent with quantum gravity. One then expects that approximate global symmetries can be quantitatively constrained by quantum gravity or swampland arguments. We provide such a bound for an important class of global symmetries: Those arising from a gauged $U(1)$ with the vector made massive via Higgsing with an axion. The latter necessarily couples to instantons, and their action can be constrained, using both the electric and magnetic version of the axionic weak gravity conjecture, in terms of the cutoff of the theory. As a result, instanton-induced symmetry breaking operators with a suppression factor not smaller than $\exp(-M_{\rm P}^2/Λ^2)$ are present, where $Λ$ is a cutoff of the 4d effective theory. We provide a general argument and clarify the meaning of $Λ$. Simple 4d and 5d models are presented to illustrate this, and we recall that this is the standard way in which things work out in string compactifications with brane instantons. The relation of our constraint to bounds that can be derived from wormholes or gravitational instantons and to those motivated by black-hole effects at finite temperature are discussed, and we present a generalization of the Giddings-Strominger wormhole solution to the case of a gauge-derived $U(1)$ global symmetry. Finally, we discuss potential loopholes to our arguments.

hep-th↗