No Arabic abstract
Cloud-based documents are inherently valuable, due to the volume and nature of sensitive personal and business content stored in them. Despite the importance of such documents to Internet users, there are still large gaps in the understanding of what cybercriminals do when they illicitly get access to them by for example compromising the account credentials they are associated with. In this paper, we present a system able to monitor user activity on Google spreadsheets. We populated 5 Google spreadsheets with fake bank account details and fake funds transfer links. Each spreadsheet was configured to report details of accesses and clicks on links back to us. To study how people interact with these spreadsheets in case they are leaked, we posted unique links pointing to the spreadsheets on a popular paste site. We then monitored activity in the accounts for 72 days, and observed 165 accesses in total. We were able to observe interesting modifications to these spreadsheets performed by illicit accesses. For instance, we observed deletion of some fake bank account information, in addition to insults and warnings that some visitors entered in some of the spreadsheets. Our preliminary results show that our system can be used to shed light on cybercriminal behavior with regards to leaked online documents.
While there has been much recent work studying how linguistic information is encoded in pre-trained sentence representations, comparatively little is understood about how these models change when adapted to solve downstream tasks. Using a suite of analysis techniques (probing classifiers, Representational Similarity Analysis, and model ablations), we investigate how fine-tuning affects the representations of the BERT model. We find that while fine-tuning necessarily makes significant changes, it does not lead to catastrophic forgetting of linguistic phenomena. We instead find that fine-tuning primarily affects the top layers of BERT, but with noteworthy variation across tasks. In particular, dependency parsing reconfigures most of the model, whereas SQuAD and MNLI appear to involve much shallower processing. Finally, we also find that fine-tuning has a weaker effect on representations of out-of-domain sentences, suggesting room for improvement in model generalization.
In the system of a gravitating Q-ball, there is a maximum charge $Q_{{rm max}}$ inevitably, while in flat spacetime there is no upper bound on $Q$ in typical models such as the Affleck-Dine model. Theoretically the charge $Q$ is a free parameter, and phenomenologically it could increase by charge accumulation. We address a question of what happens to Q-balls if $Q$ is close to $Q_{{rm max}}$. First, without specifying a model, we show analytically that inflation cannot take place in the core of a Q-ball, contrary to the claim of previous work. Next, for the Affleck-Dine model, we analyze perturbation of equilibrium solutions with $Qapprox Q_{{rm max}}$ by numerical analysis of dynamical field equations. We find that the extremal solution with $Q=Q_{{rm max}}$ and unstable solutions around it are critical solutions, which means the threshold of black-hole formation.
The mainstream textbooks of quantum mechanics explains the quantum state collapses into an eigenstate in the measurement, while other explanations such as hidden variables and multi-universe deny the collapsing. Here we propose an ideal thinking experiment on measuring the spin of an electron with 3 steps. It is simple and straightforward, in short, to measure a spin-up electron in x-axis, and then in z-axis. Whether there is a collapsing predicts different results of the experiment. The future realistic experiment will show the quantum state collapses or not in the measurement.
Roger Penroses 2020 Nobel Prize in Physics recognises that his identification of the concepts of gravitational singularity and an incomplete, inextendible, null geodesic is physically very important. The existence of an incomplete, inextendible, null geodesic doesnt say much, however, if anything, about curvature divergence, nor is it a helpful definition for performing actual calculations. Physicists have long sought for a coordinate independent method of defining where a singularity is located, given an incomplete, inextendible, null geodesic, that also allows for standard analytic techniques to be implemented. In this essay we present a solution to this issue. It is now possible to give a concrete relationship between an incomplete, inextendible, null geodesic and a gravitational singularity, and to study any possible curvature divergence using standard techniques.
We study the effect of radiation pressure on the dust in the inner rim of transitional disks with large inner holes. In particular, we evaluate whether radiation pressure can be responsible for keeping the inner holes dust-free, while allowing gas accretion to proceed. This has been proposed in a paper by Chiang and Murray-Clay (2007, Nature Physics 3, p. 604) who explain the formation of these holes as an inside-out evacuation due to X- ray-triggered accretion of the innermost layer of the disk rim outside of the hole. We show that radiation pressure is clearly incapable of stopping dust from flowing into the hole because of dust pile-up and optical depth effects, and also because of viscous mixing. Other mechanisms need to be found to explain the persistence of the opacity hole in the presence of accretion, and we speculate on possible solutions.