Pantelis S. Apostolopoulos

Drought monitoring on small islands is challenged by coastline-grid mismatch and by the possibility that meteorological recovery precedes recovery of soil-water conditions. This study presents a native-grid, area-weighted framework for the Ionian Islands using Climate Hazards Center Infrared Precipitation with Stations version 3 (CHIRPS v3), TerraClimate potential evapotranspiration, and modelled soil-water storage for 1981–2024. The framework preserves each product’s original spatial support, derives monthly island series, calculates the Standardized Precipitation Evapotranspiration Index (SPEI) at 1-, 3-, 6-, and 12-month scales, constructs a drought-event catalogue, evaluates temporal trends, and quantifies soil-water recovery. It identified 690 scale-specific events; longer accumulation scales produced fewer but more persistent events. No generalized robust intensification was detected. Full-period negative SPEI-3 signals in Kefalonia and Ithaca were sensitive to the 2020–2024 terminal period, while the remaining island trends were not significant after false discovery rate adjustment. In 34.3% of completed events, modelled soil-water storage remained below normal when SPEI first returned to nonnegative values. Recovery lags had a median of 0 months, a 90th percentile of 4 months, and a maximum of 20 months. The framework provides a transparent, transferable basis for drought monitoring and water-resource planning in insular environments.

Zakynthos is a small coastal city where environmental conditions, compact urban development, and strong seasonal tourism pressures influence everyday living conditions. This study examines how these factors shape urban quality of life (QoL) across the city using a GIS-based multicriteria framework. A literature review indexed in JSTOR, PubMed, and Scopus, completed in early 2026, guided indicator selection. Nine criteria—estimated population density, the Normalized Difference Vegetation Index (NDVI), public recreation, accessibility, Land Surface Temperature (LST), proximity to forests and the sea, road-related acoustic suitability, imperviousness, and nighttime lighting—were standardized to a 0–100 scale and combined using Analytic Hierarchy Process (AHP) weights. The analysis brings together satellite-derived environmental variables and detailed local information on buildings, recreational spaces, services, and roads on a common 10 m grid. This level of detail is particularly useful in a small Mediterranean city, a setting that remains underrepresented in GIS–AHP studies of QoL. Moderate QoL covered 30.86% of the study area, while the low and very low classes accounted for 41.24% together. Only 3.12% was classified as very high. Higher scores were primarily observed along the northern coast and in vegetated regions. In contrast, central and southwestern neighborhoods typically scored lower due to heat, impervious surfaces, traffic noise, and fewer recreational options. However, some central areas still maintain good access to services. The maps illustrate the local trade-offs between accessibility and environmental quality, providing a detailed baseline to identify zones where targeted planning actions may be necessary.

Forest managers require consistent information on wildfire extent, satellite-derived burn effects, vegetation recovery, and sites requiring field inspection. We examined how a consistent Sentinel-2 workflow in Google Earth Engine could link event delineation and re-burn-aware spectral recovery monitoring to post-fire field-verification priorities in Zakynthos, Greece, over the 2016–2025 study period. Here, recovery means change in satellite-derived vegetation indices, not independently measured ecological restoration. A screened daily minimum Normalized Burn Ratio (NBR) workflow supplied the main analyses, while a seasonal-composite workflow was retained as a conservative baseline. Cloud-screened mosaics, persistent burn evidence, and confidence screening reduced 255 candidates to 117 high- or medium-confidence events. Timing diagnostics showed that fixed July–September composites are repeatable but not event-specific post-fire observations for every fire. Differenced NBR classes were treated as indicators of spectral change, not field-validated ecological burn severity. External footprint comparisons with selected Copernicus Emergency Management Service (CEMS) references yielded screened daily workflow intersection over union of 0.867, 0.799 and 0.890 for 2017, 2019 and 2025, respectively; the comparisons were not strictly same-date. Random Forest classification showed 85.86% agreement with NBR-derived recovery classes, with similar results under event-grouped and spatial-block validation. Agreement decreased when the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Moisture Index (NDMI) recovery ratios were excluded, indicating dependence on recovery-related spectral information. High and very high priority zones covered 558.47 ha, but their extent was sensitive to weighting. The outputs support forest-service field checks for regeneration, tree and shrub condition, exposed soil, erosion indicators, and fuel continuity. They do not provide independent ecological validation and are not automatic restoration prescriptions.

In a recent paper, a new conformally flat metric was introduced, describing an expanding scalar field in a spherically symmetric geometry. The spacetime can be interpreted as a Schwarzschild-like model with an apparent horizon surrounding the curvature singularity. For the above metric, we present the complete conformal Lie algebra consisting of a six-dimensional subalgebra of isometries (Killing Vector Fields or KVFs) and nine proper conformal vector fields (CVFs). An interesting aspect of our findings is that there exists a gradient (proper) conformal symmetry (i.e., its bivector vanishes) which verifies the importance of gradient symmetries in constructing viable cosmological models. In addition, the 9-dimensional conformal algebra implies the existence of constants of motion along null geodesics that allow us to determine the complete solution of null geodesic equations.

Using purely geometrical methods we present a mechanism to solve the scalar field equations of motion (non-minimally coupled with gravity) in a spherically symmetric background. We found that the full set of spacetimes, which are of Petrov type O (conformally flat) and admit a gradient conformal vector field, can be determined completely. It is shown that the full group of scalar field equations reduced to a single equation that depends only on the distance w = r 2 − t 2 leaving the metric function (equivalently the functional form of the scalar field or the potential) freely chosen. Depending on the structure of the metric or the potential V (as a function of φ) a solution can be found either analytically or via numerical integration. We provide physically sound examples and prove that (Anti)-de Sitter fits this scheme. We also reconstruct a recently found solution (Strumia and Tetradis 2022 J. High Energy Phys. JHEP09(2022)203) representing an expanding scalar bubble with metric that has a singularity and corresponds to what is termed as Anti-de Sitter crunch.

In a recent paper, a new conformally flat metric was introduced, describing an expanding scalar field in a spherically symmetric geometry. The spacetime can be interpreted as a Schwarzschild-like model with an apparent horizon surrounding the curvature singularity. For the above metric, we present the complete conformal Lie algebra consisting of a six-dimensional subalgebra of isometries (Killing Vector Fields or KVFs) and nine proper conformal vector fields (CVFs). An interesting aspect of our findings is that there exists a gradient (proper) conformal symmetry (i.e., its bivector F_ab vanishes) which verifies the importance of gradient symmetries in constructing viable cosmological models. In addition, the 9-dimensional conformal algebra implies the existence of constants of motion along null geodesics that allow us to determine the complete solution of null geodesic equations.

In this work, we would like to address the problem of the effect of bulk matter on the brane cosmological evolution in a general way. We assume that the spatial part of the brane metric is not maximally symmetric, and is, therefore, spatially inhomogeneous. However, we retain the conformal flatness property of the standard cosmological model (FRW), i.e., the Weyl tensor of the induced 4D geometry is zero. We refer to it as Spatially Inhomogeneous Irrotational (SII) brane. It is shown that the model can be regarded as the 5D generalization of the SII spacetimes found recently.