IPBPub
Institute of Physics Belgrade
Publication Repository
Recent Submissions
Item
Investigation of VLF/LF electric field variations related to magnitude Mw≥5.5 earthquakes in the Mediterranean region for the year 2023
Hans Eichelberger; Mohammed Y. Boudjada; Konrad Schwingenschuh; Bruno P. Besser; Daniel Wolbang; Maria Solovieva; Pier F. Biagi; Patrick H. M. Galopeau; Ghulam Jaffer; Christoph Schirninger; Nina, Aleksandra; Gordana Jovanovic; Giovanni Nico; Manfred Stachel; Özer Aydogar; Cosima Muck; Josef Wilfinger; Irmgard Jernej; Werner Magnes
Strong natural hazards together with their societal impact are usually accompanied by multiple physical phenomena which can be an important information source about the underlying processes.
In this study we statistically analyze the lithosphere–atmosphere–ionosphere couplings of magnitude Mw5.5+ earthquakes (EQs) in the year 2023 with the aid of sub-ionospheric VLF/LF radio links. The electric field amplitude and phase measurements with a temporal resolution of one second are from the seismo-electromagnetic receiver facility in Graz (GRZ), Austria (Galopeau et al., 2023), which is part of the INFREP network. The spatial extend of the study area has the range [-10°E ≤ longitude ≤ 40°E] and [20°N ≤ latitude ≤ 50°N], in total are 17 EQs according to the United States Geological Survey (USGS) data base, among them the Turkey–Syria EQs (main shocks Mw7.8 and Mw7.5) and the Morocco Mw6.8 EQ. We apply the night-time amplitude method (Hayakawa et al., 2010) for all available paths, of particular importance are the transmitter links TBB (26.70 kHz, Bafa, Turkey), ITS (45.90 kHz, Niscemi, Sicily, Italy), and ICV (20.27 kHz, Tavolara, Italy). Relevant crossings are determined by the size of the Dobrovolsky-Bowman relationship (Dobrovolsky et al., 1979; Bowman et al., 1998).
A major finding is the statistically significant electric field variation of the TBB-GRZ link related to the Turkey–Syria EQ sequence. A physical interpretation is based on atmospheric gravity waves (AGWs) which could alter the E-layer in the lower ionosphere during nighttime and modulate the height of the waveguide cavity.
Item
The Study of Percolation with the Presence of Extended Impurities
Lončarević, Ivana; Budinski-Petković, Ljuba; Dujak, Dijana; Karač, Aleksandar; Jakšić, Zorica; Vrhovac, Slobodan
In the preceding paper, Budinski-Petković et al (2016 J. Stat. Mech. 053101) studied jamming and percolation aspects of random sequential adsorption of extended shapes onto a triangular lattice initially covered with point-like impurities at various concentrations. Here we extend this analysis to needle-like impurities of various lengths ℓ. For a wide range of impurity concentrations p, percolation threshold θp∗ is determined for k-mers, angled objects and triangles of two different sizes. For sufficiently large impurities, percolation threshold θp∗ of all examined objects increases with concentration p, and this increase is more prominent for impurities of a larger length ℓ. We determine the critical concentrations of pc∗ defects above which it is not possible to achieve percolation for a given object, for impurities of various lengths ℓ. It is found that the critical concentration pc∗ of finite-size impurities decreases with the length ℓ of impurities. In the case of deposition of larger objects an exception occurs for point-like impurities when critical concentration pc∗ of monomers is lower than pc∗ for the dimer impurities. At relatively low concentrations p, the presence of small impurities (but not point-like) stimulates the percolation for larger depositing objects.
Item
Fierz Convergence Criterion: A Controlled Approach to Strongly Interacting Systems with Small Embedded Clusters
Ayral, Thomas; Vučičević, Jakša; Parcollet, Olivier
We present an embedded-cluster method, based on the triply irreducible local expansion formalism. It turns the Fierz ambiguity, inherent to approaches based on a bosonic decoupling of local fermionic interactions, into a convergence criterion. It is based on the approximation of the three-leg vertex by a coarse-grained vertex computed from a self-consistently determined cluster impurity model. The computed self-energies are, by construction, continuous functions of momentum. We show that, in three interaction and doping regimes of the two-dimensional Hubbard model, self-energies obtained with clusters of size four only are very close to numerically exact benchmark results. We show that the Fierz parameter, which parametrizes the freedom in the Hubbard-Stratonovich decoupling, can be used as a quality control parameter. By contrast, the GW+extended dynamical mean field theory approximation with four cluster sites is shown to yield good results only in the weak-coupling regime and for a particular decoupling. Finally, we show that the vertex has spatially nonlocal components only at low Matsubara frequencies.
Item
Quantum criticality in photorefractive optics: Vortices in laser beams and antiferromagnets
Čubrović, Mihailo; Petrović, Milan
We study vortex patterns in a prototype nonlinear optical system: counterpropagating laser beams in a photorefractive crystal, with or without the background photonic lattice. The vortices are effectively planar and have two "flavors" because there are two opposite directions of beam propagation. In a certain parameter range, the vortices form stable equilibrium configurations which we study using the methods of statistical field theory and generalize the Berezinsky-Kosterlitz-Thouless transition of the XY model to the "two-flavor" case. In addition to the familiar conductor and insulator phases, we also have the perfect conductor (vortex proliferation in both beams or "flavors") and the frustrated insulator (energy costs of vortex proliferation and vortex annihilation balance each other). In the presence of disorder in the background lattice, a phase appears which shows long-range correlations and absence of long-range order, thus being analogous to glasses. An important benefit of this approach is that qualitative behavior of patterns can be known without intensive numerical work over large areas of the parameter space. The observed phases are analogous to those in magnetic systems, and make (classical) photorefractive optics a fruitful testing ground for (quantum) condensed matter systems. As an example, we map our system to a doped O(3) antiferromagnet with Z2 defects, which has the same structure of the phase diagram.
Item
Entanglement spectrum of the degenerative ground state of Heisenberg ladders in a time-dependent magnetic field
Predin, Sonja
We investigate the relationship between the entanglement and subsystem Hamiltonians in the perturbative regime of strong coupling between subsystems. One of the two conditions that guarantees the proportionality between these Hamiltonians obtained by using the nondegenerate perturbation theory within the first order is that the unperturbed ground state has a trivial entanglement Hamiltonian. Furthermore, we study the entanglement Hamiltonian of the Heisenberg ladders in a time-dependent magnetic field using the degenerate perturbation theory, where couplings between legs are considered as a perturbation. In this case, when the ground state is twofold degenerate, and the entanglement Hamiltonian is proportional to the Hamiltonian of a chain within first-order perturbation theory, even then also the unperturbed ground state has a nontrivial entanglement spectrum.