Spacetime Defects and Bouncing Cosmology

Bis zum heutigen Tag ist die allgemeine Relativitätstheorie weithin als die relevante Theorie der Gravitation anerkannt und wurde durch viele Experimente bestätigt. Trotz dieses Erfolges liefert die allgemeine Relativitätstheorie keine Antwort auf viele offene Fragen, die mit Gravitation zusammenhängen. Das endgültige Schicksal scheinbarer Raumzeit-Singularitäten ist eine dieser offenen Fragen. Mögliche Lösungen für Raumzeit-Singularitäten werden in dieser Arbeit diskutiert. In diesen speziellen Lösungen werden Singularitäten durch Raumzeitdefekte ersetzt: Die Singularität des Schwarzen Loches wird durch einen Raumdefekt und die Urknall-Singularität wird durch einen Zeitdefekt ersetzt. In dieser Arbeit untersuchen wir bestimmte Effekte, die Raumzeitdefekte verursachen könnten. Wir berechnen die Geodäten der Raumzeitdefekte. Für den Raumdefekt diskutieren wir seine Linseneigenschaften und die entsprechende Bilderzeugung. Für den Zeitdefekt untersuchen wir die entsprechende nicht singuläre prallende Kosmologie. Wir präsentieren auch einige mögliche beobachtbare Effekte im Zusammenhang mit den Raumzeitdefekten

A Dual Latent State Learning Approach: Exploiting Regional Network Similarities for QoS Prediction

Individual objects, whether users or services, within a specific region often exhibit similar network states due to their shared origin from the same city or autonomous system (AS). Despite this regional network similarity, many existing techniques overlook its potential, resulting in subpar performance arising from challenges such as data sparsity and label imbalance. In this paper, we introduce the regional-based dual latent state learning network(R2SL), a novel deep learning framework designed to overcome the pitfalls of traditional individual object-based prediction techniques in Quality of Service (QoS) prediction. Unlike its predecessors, R2SL captures the nuances of regional network behavior by deriving two distinct regional network latent states: the city-network latent state and the AS-network latent state. These states are constructed utilizing aggregated data from common regions rather than individual object data. Furthermore, R2SL adopts an enhanced Huber loss function that adjusts its linear loss component, providing a remedy for prevalent label imbalance issues. To cap off the prediction process, a multi-scale perception network is leveraged to interpret the integrated feature map, a fusion of regional network latent features and other pertinent information, ultimately accomplishing the QoS prediction. Through rigorous testing on real-world QoS datasets, R2SL demonstrates superior performance compared to prevailing state-of-the-art methods. Our R2SL approach ushers in an innovative avenue for precise QoS predictions by fully harnessing the regional network similarities inherent in objects

Sex difference in the effect of Internet gaming disorder on the brain functions: evidence from resting-state fMRI

Objective: Studies have shown that males are more prevalence than females in Internet gaming disorder (IGD). This study was set to explore the sex difference on the effect of IGD in resting states of the brain. Methods: Resting-state fMRI data were collected from 58 recreational Internet game users (RGU, male = 29) and 46 IGD subjects (male = 23). Regional homogeneity (ReHo) was used to calculate group difference between the subjects. A two-way ANOVA was used to explore the IGD-by-sex interactions. Correlations between addiction severity and the ReHo values were also calculated. Results: Significant sex-by-group interactions were found associated with the brain features in the right posterior cingulate (rPCC), left middle occipital gyrus (lMOG), right middle temporal gyrus (rMTG), and right postcentral gyrus (rPG). Post-hoc analysis revealed that comparing with same-sex RGUs, male IGD showed decreased ReHo in the rPCC, and the ReHo in the rPCC was also negatively associated with Internet addiction test (IAT) scores for male subjects. Moreover, male IGDs showed increased ReHo, but female ones showed decreased ReHo, in both lMOG and rMTG, when comparing with same-sex RGUs. Conclusions: Sex differences were observed in brain regions that are responsible for executive control, visual and auditory perception. These sex differences should be taken into consideration in future studies and the treatment of IGD

Atomically phase-matched second-harmonic generation in a 2D crystal.

Second-harmonic generation (SHG) has found extensive applications from hand-held laser pointers to spectroscopic and microscopic techniques. Recently, some cleavable van der Waals (vdW) crystals have shown SHG arising from a single atomic layer, where the SH light elucidated important information such as the grain boundaries and electronic structure in these ultra-thin materials. However, despite the inversion asymmetry of the single layer, the typical crystal stacking restores inversion symmetry for even numbers of layers leading to an oscillatory SH response, drastically reducing the applicability of vdW crystals such as molybdenum disulfide (MoS2). Here, we probe the SHG generated from the noncentrosymmetric 3R crystal phase of MoS2. We experimentally observed quadratic dependence of second-harmonic intensity on layer number as a result of atomically phase-matched nonlinear dipoles in layers of the 3R crystal that constructively interfere. By studying the layer evolution of the A and B excitonic transitions in 3R-MoS2 using SHG spectroscopy, we also found distinct electronic structure differences arising from the crystal structure and the dramatic effect of symmetry and layer stacking on the nonlinear properties of these atomic crystals. The constructive nature of the SHG in this 2D crystal provides a platform to reliably develop atomically flat and controllably thin nonlinear media