7,659 research outputs found
Fixed conjugacy classes of normal subgroups and the k(GV)-problem
We establish several new bounds for the number of conjugacy classes of a
finite group, all of which involve the maximal number c of conjugacy classes of
a normal subgroup fixed by some element of a suitable subset of the group. To
apply these formulas effectively, the parameter c, which in general is hard to
control, is studied in some important situations. These results are then used
to provide a new, shorter proof of the most difficult case of the well-known
k(GV)-problem, which occurs for p=5 and V induced from the natural module of a
5-complement of GL(2,5). We also show how, for large p, the new results reduce
the k(GV)-problem to the primitive case, thereby improving previous work on
this. Furthermore, we discuss how they can be used in tackling the imprimitive
case of the as of yet unsolved noncoprime k(GV)-problem
Modeling Task Effects in Human Reading with Neural Attention
Humans read by making a sequence of fixations and saccades. They often skip
words, without apparent detriment to understanding. We offer a novel
explanation for skipping: readers optimize a tradeoff between performing a
language-related task and fixating as few words as possible. We propose a
neural architecture that combines an attention module (deciding whether to skip
words) and a task module (memorizing the input). We show that our model
predicts human skipping behavior, while also modeling reading times well, even
though it skips 40% of the input. A key prediction of our model is that
different reading tasks should result in different skipping behaviors. We
confirm this prediction in an eye-tracking experiment in which participants
answers questions about a text. We are able to capture these experimental
results using the our model, replacing the memorization module with a task
module that performs neural question answering
A Taxonomy for Attack Patterns on Information Flows in Component-Based Operating Systems
We present a taxonomy and an algebra for attack patterns on component-based
operating systems. In a multilevel security scenario, where isolation of
partitions containing data at different security classifications is the primary
security goal and security breaches are mainly defined as undesired disclosure
or modification of classified data, strict control of information flows is the
ultimate goal. In order to prevent undesired information flows, we provide a
classification of information flow types in a component-based operating system
and, by this, possible patterns to attack the system. The systematic
consideration of informations flows reveals a specific type of operating system
covert channel, the covert physical channel, which connects two former isolated
partitions by emitting physical signals into the computer's environment and
receiving them at another interface.Comment: 9 page
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