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Spot-crossing transits offer a unique opportunity to probe spot properties such as temperature, size, and surface distribution. TOI-3884 is a rare system in which spot-crossing features are persistently observed during every transit. This is due to its unusual configuration: a nearly poler orbit super-Neptune transits a pole-on mid-M dwarf, repeatedly crossing a polar spot. However, previous studies have reported discrepant values in key system parameters, such as stellar inclination and obliquity. To address this, we conducted multi-band, multi-epoch transit observations of TOI-3884b using the MuSCAT instrument series, along with photometric monitoring with the LCO 1m telescopes/Sinistro. We detected time-dependent variations in the spot-crossing signals, indicating that the spot is not exactly on the pole. From the monitoring data, we measured a stellar rotation period of $11.043~_{-0.053}^{+0.054}$ days with a modulation amplitude of $\sim$5% in the r-band, consistent with the time variability in the spot-crossing features. Our analysis reconciles previous discrepancies and improves the constraints on the parameters of the system geometry ($i_\star = 139.9~^{+1.2}_{-2.0}$ deg an

Understanding the dynamics of excitation patterns in neural fields is an important topic in neuroscience. Neural field equations are mathematical models that describe the excitation dynamics of interacting neurons to perform the theoretical analysis. Although many analyses of neural field equations focus on the effect of neuronal interactions on the flat surface, the geometric constraint of the dynamics is also an attractive topic when modeling organs such as the brain. This paper reports pattern dynamics in a neural field equation defined on spheroids as model curved surfaces. We treat spot solutions as localized patterns and discuss how the geometric properties of the curved surface change their properties. To analyze spot patterns on spheroids with small flattening, we first construct exact stationary spot solutions on the spherical surface and reveal their stability. We then extend the analysis to show the existence and stability of stationary spot solutions in the spheroidal case. One of our theoretical results is the derivation of a stability criterion for stationary spot solutions localized at poles on oblate spheroids. The criterion determines whether a spot solution remain

Sweeping beams of light can cast spots moving with superluminal speeds across scattering surfaces. Such faster-than-light speeds are well-known phenomena that do not violate special relativity. It is shown here that under certain circumstances, superluminal spot pair creation and annihilation events can occur that provide unique information to observers. These spot pair events are {\it not} particle pair events -- they are the sudden creation or annihilation of a pair of relatively illuminated spots on a scattering surface. Real spot pair illumination events occur unambiguously on the scattering surface when spot speeds diverge, while virtual spot pair events are observer dependent and perceived only when real spot radial speeds cross the speed of light. Specifically, a virtual spot pair creation event will be observed when a real spot's speed toward the observer drops below $c$, while a virtual spot pair annihilation event will be observed when a real spot's radial speed away from the observer rises above $c$. Superluminal spot pair events might be found angularly, photometrically, or polarimetrically, and might carry useful geometry or distance information. Two example scenarios

Parking functions correspond with preferences of $n$ cars which enter sequentially to park on a one-way street where (1) each car parks in the first available spot greater than or equal to its preference and (2) all cars successfully park. When a car parks in its preferred spot then the corresponding car and corresponding spot are deemed ``lucky.'' This paper looks briefly at lucky cars which have previously been studied and in simple cases can be understood by a generalization of a result due to Pollak. We also consider lucky spots where the situation is more complex and not previously studied. Probabilities and asymptotics for lucky spots are given for the first few spots on the one-way street. We close with an exploration of the special cases when cars enter the one-way street in either weakly-increasing or weakly-decreasing order of their preferences.

Betas from spot regressions are central to asset pricing and risk management, as measures of systematic risk. This paper develops a new estimation and inference framework for spot regressions by leveraging high-frequency candlesticks, extending conventional (open-to-close) returns with intra-period high/low prices. Specifically, I construct candlestick-based estimators of regression parameters, including spot beta, by minimizing a quadratic risk under a fixed-k asymptotic framework. I then develop a feasible hypothesis testing procedure for spot betas with correct asymptotic size. Simulation results show that the proposed estimator reduces estimation risk relative to return-based estimators, especially in small samples, and the test achieves notably higher power. I apply the framework to assess the market neutrality of Bitcoin using 1-minute data on IBIT and SPY, finding deviations from neutrality, particularly in high-volatility periods.

Age spots are the brown spots that develop in the skin but change in color and shape with time. To understand the mechanism of development of age spots, characteristics of age spots are analyzed by Misrepair mechanism, a mechanism introduced in Misrepair-accumulation aging theory. An age spot is pathologically a group of aggregated basal cells, which contain lipofuscin bodies. Accumulation of lipofuscin bodies is a sign of aging of a cell. Characteristics of age spots include: inhomogeneity in distribution, growing flatly before becoming protruding, irregularity on shape, inhomogeneity on the color and on the protruding degree of a spot, and softness of a protruding spot. After analyzing these characteristics, we make a hypothesis on the process of development of an age spot. A. Aging of a tissue is the basis for development of age spots. B. A flat spot results from accumulation of lipofuscin containing cells. When an aged cell remains, this cell can accelerate the aging of its neighbor cells by increasing damage sensitivity and reducing repair efficiency of the local tissue. By a viscous circle, more and more neighbor cells become aged and they form a flat spot, which has an irreg

Spot is a mature, open-source C++/Python library and toolset for Linear Temporal Logic (LTL) and $ω$-automata manipulation. While Spot is routinely used as a research and verification back-end, its rich visualization capabilities and Python interface also make it an attractive platform for \emph{teaching} the connections between temporal logic formulas and the $ω$-automata that give them their semantics.

While Vision Transformers (ViT) have demonstrated remarkable performance across diverse tasks, their computational demands are substantial, scaling quadratically with the number of processed tokens. Compact attention representations, reflecting token interaction distributions, can guide early detection and reduction of less salient tokens prior to attention computation. Motivated by this, we present SParsification with attentiOn dynamics via Token relevance (SPOT), a framework for early detection of redundant tokens within ViTs that leverages token embeddings, interactions, and attention dynamics across layers to infer token importance, resulting in a more context-aware and interpretable relevance detection process. SPOT informs token sparsification and facilitates the elimination of such tokens, improving computational efficiency without sacrificing performance. SPOT employs computationally lightweight predictors that can be plugged into various ViT architectures and learn to derive effective input-specific token prioritization across layers. Its versatile design supports a range of performance levels adaptable to varying resource constraints. Empirical evaluations demonstrate sig

We systematically examine light curves from a single hot spot on a slowly rotating neutron star with very high compactness, where the so-called invisible zone does not exist. In particular, we adopt three different shapes of hot spot and take into account the finite size effect of hot spot on the light curves. Then, we find that the brightening of flux occurs when the hot spot with small area crosses the opposite side to the observer, where the brightening becomes stronger as the area of hot spot decreases. Since this brightening happens only when a part of hot spot crosses the opposite side to the observer, one may constrain the neutron star geometry, i.e., the combination of an inclination angle, angle between the rotational axis and normal vector at the center of hot spot, and the opening angle of hot spot, if the brightening would be observed. In addition, by counting such a brightening in the light curves, one may know how many narrow bands of hot spot and/or spots with small area cross the opposite side to the observer.

Vision Transformers naturally accommodate sparsity, yet standard tokenization methods confine features to discrete patch grids. This constraint prevents models from fully exploiting sparse regimes, forcing awkward compromises. We propose Subpixel Placement of Tokens (SPoT), a novel tokenization strategy that positions tokens continuously within images, effectively sidestepping grid-based limitations. With our proposed oracle-guided search, we uncover substantial performance gains achievable with ideal subpixel token positioning, drastically reducing the number of tokens necessary for accurate predictions during inference. SPoT provides a new direction for flexible, efficient, and interpretable ViT architectures, redefining sparsity as a strategic advantage rather than an imposed limitation.

An extremely cold and big spot in the WMAP 1-year data is analyzed. Our work is a continuation of a previous paper (Vielva et al. 2004) where non-Gaussianity was detected, with a method based on the Spherical Mexican Hat Wavelet (SMHW) technique. We study the spots at different thresholds on the SMHW coefficient maps, considering six estimators, namely number of maxima, number of minima, number of hot and cold spots, and number of pixels of the spots. At SMHW scales around 4 degrees (10 degrees on the sky), the data deviate from Gaussianity. The analysis is performed on all sky, the northern and southern hemispheres, and on four regions covering all the sky. A cold spot at (b = -57, l = 209) is found to be the source of this non-Gaussian signature. We compare the spots of our data with 10000 Gaussian simulations, and conclude that only around 0.2% of them present such a cold spot. Excluding this spot, the remaining map is compatible with Gaussianity and even the excess of kurtosis in Vielva et al. 2004, is found to be due exclusively to this spot. Finally, we study whether the spot causing the observed deviation from Gaussianity could be generated by systematics or foregrounds. Non

Cool spots on the surface of magnetically-active stars modulate their observed brightnesses and temperatures, thereby affecting the stellar locus on the H-R diagram. Recent high precision space-based photometric surveys reveal the rotational modulation from spots on stars in young clusters, including K2 monitoring of the 125-Myr-old Pleiades cluster. However, lightcurves reveal only the asymmetries in the visible spot distributions rather than the total sizes of spots on stellar surfaces, which causes a discrepancy between the spot coverage measured by photometric and spectroscopic observations. In this paper, we simulate photometric variability introduced by randomly-distributed starspots on a 125-Myr-old coeval cluster. Our simulation results show that randomly distributed small spots on the stellar surface would explain this discrepancy that the photometric observations only reveal 10% to 40% of the spot coverage measured by spectra. The colors and luminosities of photospheres are modeled for a range of photospheric temperature, spot coverage, and spot temperature. The colors and luminosities of a simulated population are then compared to the luminosity spread of Pleiades member

In this work, we investigate if gravitational microlensing can magnify the polarization signal of a stellar spot and make it be observable. A stellar spot on a source star of microlensing makes polarization signal through two channels of Zeeman effect and breaking circular symmetry of the source surface brightness due to its temperature contrast. We first explore the characteristics of perturbations in polarimetric microlensing during caustic-crossing of a binary lensing as follows: (a) The cooler spots over the Galactic bulge sources have the smaller contributions in the total flux, although they have stronger magnetic fields. (b) The maximum deviation in the polarimetry curve due to the spot happens when the spot is located near the source edge and the source spot is first entering the caustic whereas the maximum photometric deviation occurs for the spots located at the source center. (c) There is a (partial) degeneracy for indicating spot's size, its temperature contrast and its magnetic induction from the deviations in light or polarimetric curves. (d) If the time when the photometric deviation due to spot becomes zero (between positive and negative deviations) is inferred from

During microlensing events with a small impact parameter, the amplification of the source flux is sensitive to the surface brightness distribution of the source star. Such events provide a means for studying the surface structure of target stars in the ongoing microlensing surveys, most efficiently for giants in the Galactic bulge. In this work we demonstrate the sensitivity of point-mass microlensing to small spots with radii $r_s\lesssim0.2$ source radii. We compute the amplification deviation from the light curve of a spotless source and explore its dependence on lensing and spot parameters. During source-transit events spots can cause deviations larger than 2%, and thus be in principle detectable. Maximum relative deviation usually occurs when the lens directly crosses the spot. Its numerical value for a dark spot with sufficient contrast is found to be roughly equal to the fractional radius of the spot, i.e., up to 20% in this study. Spots can also be efficiently detected by the changes in sensitive spectral lines during the event. Notably, the presence of a spot can mimic the effect of a low-mass companion of the lens in some events.

Cloud spot markets rent VMs for a variable price that is typically much lower than the price of on-demand VMs, which makes them attractive for a wide range of large-scale applications. However, applications that run on spot VMs suffer from cost uncertainty, since spot prices fluctuate, in part, based on supply, demand, or both. The difficulty in predicting spot prices affects users and applications: the former cannot effectively plan their IT expenditures, while the latter cannot infer the availability and performance of spot VMs, which are a function of their variable price. To address the problem, we use properties of cloud infrastructure and workloads to show that prices become more stable and predictable as they are aggregated together. We leverage this observation to define an aggregate index price for spot VMs that serves as a reference for what users should expect to pay. We show that, even when the spot prices for individual VMs are volatile, the index price remains stable and predictable. We then introduce cloud index tracking: a migration policy that tracks the index price to ensure applications running on spot VMs incur a predictable cost by migrating to a new spot VM if

Recognizing places from an opposing viewpoint during a return trip is a common experience for human drivers. However, the analogous robotics capability, visual place recognition (VPR) with limited field of view cameras under 180 degree rotations, has proven to be challenging to achieve. To address this problem, this paper presents Same Place Opposing Trajectory (SPOT), a technique for opposing viewpoint VPR that relies exclusively on structure estimated through stereo visual odometry (VO). The method extends recent advances in lidar descriptors and utilizes a novel double (similar and opposing) distance matrix sequence matching method. We evaluate SPOT on a publicly available dataset with 6.7-7.6 km routes driven in similar and opposing directions under various lighting conditions. The proposed algorithm demonstrates remarkable improvement over the state-of-the-art, achieving up to 91.7% recall at 100% precision in opposing viewpoint cases, while requiring less storage than all baselines tested and running faster than all but one. Moreover, the proposed method assumes no a priori knowledge of whether the viewpoint is similar or opposing, and also demonstrates competitive performanc

The spot pricing scheme has been considered to be resource-efficient for providers and cost-effective for consumers in the Cloud market. Nevertheless, unlike the static and straightforward strategies of trading on-demand and reserved Cloud services, the market-driven mechanism for trading spot service would be complicated for both implementation and understanding. The largely invisible market activities and their complex interactions could especially make Cloud consumers hesitate to enter the spot market. To reduce the complexity in understanding the Cloud spot market, we decided to reveal the backend information behind spot price variations. Inspired by the methodology of reverse engineering, we developed a Predator-Prey model that can simulate the interactions between demand and resource based on the visible spot price traces. The simulation results have shown some basic regular patterns of market activities with respect to Amazon's spot instance type m3.large. Although the findings of this study need further validation by using practical data, our work essentially suggests a promising approach (i.e.~using a Predator-Prey model) to investigate spot market activities.

The evolution of turbulent spots in a parallel shear flow is studied by means of full three-dimensional numerical simulations. The flow is bounded by free surfaces and driven by a volume force. Three regions in the spanwise spot cross-section can be identified: a turbulent interior, an interface layer with prominent streamwise streaks and vortices and a laminar exterior region with a large scale flow induced by the presence of the spot. The lift-up of streamwise streaks which is caused by non-normal amplification is clearly detected in the region adjacent to the spot interface. The spot can be characterized by an exponentially decaying front that moves with a speed different from that of the cross-stream outflow or the spanwise phase velocity of the streamwise roll pattern. Growth of the spots seems to be intimately connected to the large scale outside flow, for a turbulent ribbon extending across the box in downstream direction does not show the large scale flow and does not grow. Quantitatively, the large scale flow induces a linear instability in the neighborhood of the spot, but the associated front velocity is too small to explain the spot spreading.

The dynamics and stability of multi-spot patterns to the Gray-Scott (GS) reaction-diffusion model in a two-dimensional domain is studied in the singularly perturbed limit of small diffusivity $ε$ of one of the two solution components. A hybrid asymptotic-numerical approach based on combining the method of matched asymptotic expansions with the detailed numerical study of certain eigenvalue problems is used to predict the dynamical behavior and instability mechanisms of multi-spot quasi-equilibrium patterns for the GS model in the limit $ε\to 0$. A differential algebraic ODE system for the collective coordinates $S_j$ and ${\mathbf x}_j$ for $j=1,...,k$ is derived, which characterizes the slow dynamics of a spot pattern. Instabilities of the multi-spot pattern due to the three distinct mechanisms of spot self-replication, spot oscillation, and spot annihilation, are studied by first deriving certain associated eigenvalue problems by using singular perturbation techniques. From a numerical computation of the spectrum of these eigenvalue problems, phase diagrams representing in the GS parameter space corresponding to the onset of spot instabilities are obtained for various simple spat