arXiv subjects

Themistocles Zikopoulos

Publications and source records attributed to Themistocles Zikopoulos.

3 recordsLinked to original sources

arXiv2026

Toward the Structure Constants of $\mathcal{N}=2$ Liouville Theory

We discuss the structure constants of spacelike $\mathcal{N}=2$ Liouville theory on the two-sphere. Due to the absence of a particular $b \leftrightarrow b^{-1}$ self-dual symmetry, where $b$ is the theory's coupling, the standard analytic bootstrap toolkit that was used to solve the bosonic and $\mathcal{N}=1$ theories cannot be implemented in a straightforward way. Our approach, instead, relies on the fact that $\mathcal{N}=2$ Liouville theory is dual by mirror symmetry to the $\mathrm{SL}(2)_k/\mathrm{U}(1)$ supercoset, whose target space is the $2$d fermionic black hole. Leveraging this duality, we obtain explicit expressions for the winding number preserving and violating structure constants on the supercoset side, and test them on the Liouville side through a semiclassical analysis finding agreement up to one-loop order. We also discuss the chiral rings of the theory and evaluate correlators of $\frac 12$-BPS operators.

hep-th↗

arXiv2026

Conformal Boundary Conditions and Higher Curvature Gravity

We initiate a systematic study of Einstein-Gauss-Bonnet gravity in the presence of boundaries subject to conformal boundary conditions, in which the conformal class of the boundary metric is kept fixed. In Einstein gravity, the trace of the extrinsic curvature is also fixed at the boundary. Here we generalize this boundary condition with the appropriate higher curvature correction. We study the problem both in Euclidean and Lorentzian signature. In Euclidean signature, we show that, similarly to the Einstein gravity case, the entropy at large temperatures exhibits the behavior of a conformal field theory in one lower dimension. We also show that in the flat space limit, the higher curvature corrections do not contribute to the leading behavior at high temperatures. We conjecture that this result is a universal feature of the flat space limit in the presence of conformal boundaries. We test our conjecture by analyzing charged black holes. In Lorentzian signature, we analyze the dynamics of the boundary Weyl factor in black hole backgrounds at the linearized level.

hep-th↗

arXiv2024

Higher-Order Analysis of Three-Dimensional Anisotropy in Imbalanced Alfvénic Turbulence

We analyze in-situ observations of imbalanced solar wind turbulence to evaluate MHD turbulence models grounded in "Critical Balance" (CB) and "Scale-Dependent Dynamic Alignment" (SDDA). At energy injection scales, both outgoing and ingoing modes exhibit a weak cascade; a simultaneous tightening of SDDA is noted. Outgoing modes persist in a weak cascade across the inertial range, while ingoing modes shift to a strong cascade at $λ\approx 3 \times 10^{4} d_i$, with associated spectral scalings deviating from expected behavior due to "anomalous coherence" effects. The inertial range comprises two distinct sub-inertial segments. Beyond $λ\gtrsim 100 d_i$, eddies adopt a field-aligned tube topology, with SDDA signatures mainly evident in high amplitude fluctuations. The scaling exponents $ζ_{n}$ of the $n$-th order conditional structure functions, orthogonal to both the local mean field and fluctuation direction, align with the analytical models of Chandran et al. 2015 and Mallet et al. 2017, indicating "multifractal" statistics and strong intermittency; however, scaling in parallel and displacement components is more concave than predicted, possibly influenced by expansion effects. Below $λ\approx 100 d_i$, eddies become increasingly anisotropic, evolving into thin current sheet-like structures. Concurrently, $ζ_{n}$ scales linearly with order, marking a shift towards "monofractal" statistics. At $λ\approx 8 d_i$, the increase in aspect ratio halts, and the eddies become quasi-isotropic. This change may signal tearing instability, leading to reconnection, or result from energy redirection into the ion-cyclotron wave spectrum, aligning with the "helicity barrier". Our analysis utilizes 5-point structure functions, proving more effective than the traditional 2-point method in capturing steep scaling behaviors at smaller scales.

physics.space-ph↗