78,853 research outputs found
RiffleScrambler - a memory-hard password storing function
We introduce RiffleScrambler: a new family of directed acyclic graphs and a
corresponding data-independent memory hard function with password independent
memory access. We prove its memory hardness in the random oracle model.
RiffleScrambler is similar to Catena -- updates of hashes are determined by a
graph (bit-reversal or double-butterfly graph in Catena). The advantage of the
RiffleScrambler over Catena is that the underlying graphs are not predefined
but are generated per salt, as in Balloon Hashing. Such an approach leads to
higher immunity against practical parallel attacks. RiffleScrambler offers
better efficiency than Balloon Hashing since the in-degree of the underlying
graph is equal to 3 (and is much smaller than in Ballon Hashing). At the same
time, because the underlying graph is an instance of a Superconcentrator, our
construction achieves the same time-memory trade-offs.Comment: Accepted to ESORICS 201
SUSY dark matter(s)
We review here the status of different dark matter candidates in the context
of supersymmetric models, in particular the neutralino as a realization of the
WIMP-mechanism and the gravitino. We give a summary of the recent bounds in
direct and indirect detection and also of the LHC searches relevant for the
dark matter question. We discuss also the implications of the Higgs discovery
for the supersymmetric dark matter models and give the prospects for the future
years.Comment: 16 pages, 3 figure
Repeated aeolian deflation during the Allerød/GI-1a-c in the coversand lowland of NW Belgium
The results of multi-disciplinary research carried out on the deposits of the Moerbeke "Driehoek" site, located along the northern bank of the extensive Moervaart palaeolake (NW Belgium), are presented. The multi-proxy study, including sedimentological (organic matter, calcium carbonate and grain-size) and botanical (pollen, macrofossils, NPP) analyses, provided evidence of repeated aeolian deflation during the Allerod. Our results demonstrate, in combination with evidence from other soil archives within the Moervaart area, that the Allerod period in NW Europe was sedimentologically much less stable than hitherto assumed, especially during the GI-1c2 event and middle Allerod. Some of the Allerod deflation events were caused by centennial abrupt climatic oscillations, such as the short but pronounced cold GI-1c2 event, while others were likely the result of intense forest fires or a combination of both. These observations call for a revision of the existing Lateglacial litho- and chronostratigraphic schemes for the sand-belt of northern Europe
Determining Dark Matter properties with a XENONnT/LZ signal and LHC-Run3 mono-jet searches
We develop a method to forecast the outcome of the LHC Run 3 based on the
hypothetical detection of signal events at XENONnT. Our
method relies on a systematic classification of renormalisable single-mediator
models for dark matter-quark interactions, and is valid for dark matter
candidates of spin less than or equal to one. Applying our method to simulated
data, we find that at the end of the LHC Run 3 only two mutually exclusive
scenarios would be compatible with the detection of signal
events at XENONnT. In a first scenario, the energy distribution of the signal
events is featureless, as for canonical spin-independent interactions. In this
case, if a mono-jet signal is detected at the LHC, dark matter must have spin
1/2 and interact with nucleons through a unique velocity-dependent operator. If
a mono-jet signal is not detected, dark matter interacts with nucleons through
canonical spin-independent interactions. In a second scenario, the spectral
distribution of the signal events exhibits a bump at non zero recoil energies.
In this second case, a mono-jet signal can be detected at the LHC Run 3, dark
matter must have spin 1/2 and interact with nucleons through a unique
momentum-dependent operator. We therefore conclude that the observation of
signal events at XENONnT combined with the detection, or the
lack of detection, of a mono-jet signal at the LHC Run 3 would significantly
narrow the range of possible dark matter-nucleon interactions. As we argued
above, it can also provide key information on the dark matter particle spin.Comment: 17 pages, 8 figures, updated operator coefficients and figures,
version accepted by PR
Gully cut- and- fill cycles as related to agromanagement : a historical curve number simulation in the Tigray Highlands
Gully cut-and-fill dynamics are often thought to be driven by climate and/or deforestation related to population pressure. However, in this case-study of nine representative catchments in the Northern Ethiopian Highlands, we find that neither climate changes nor deforestation can explain gully morphology changes over the twentieth century. Firstly, by using a Monte Carlo simulation to estimate historical catchment-wide curve numbers, we show that the landscape was already heavily degraded in the nineteenth and early twentieth century – a period with low population density. The mean catchment-wide curve number (> 80) one century ago was, under the regional climatic conditions, already resulting in considerable simulated historical runoff responses. Secondly, twentieth century land-cover and runoff coefficient changes were confronted with twentieth century changing gully morphologies. As the results show, large-scale land-cover changes and deforestation cannot explain the observed processes. The study therefore invokes interactions between authigenic factors, small-scale plot boundary changes, cropland management and sociopolitical forces to explain the gully cut processes. Finally, semi-structured interviews and sedistratigraphic analysis of three filled gullies confirm the dominant impact of (crop)land management (tillage, check dams in gullies and channel diversions) on gully cut-and-fill processes. Since agricultural land management – including land tenure and land distribution – has been commonly neglected in earlier related research, we argue therefore that it can be a very strong driver of twentieth century gully morphodynamics
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