96,422 research outputs found
Superbalance of holographic entropy inequalities
The domain of allowed von Neumann entropies of a holographic field theory carves out a polyhedral cone — the holographic entropy cone — in entropy space. Such polyhedral cones are characterized by their extreme rays. For an arbitrary number of parties, it is known that the so-called perfect tensors are extreme rays. In this work, we constrain the form of the remaining extreme rays by showing that they correspond to geometries with vanishing mutual information between any two parties, ensuring the absence of Bell pair type entanglement between them. This is tantamount to proving that besides subadditivity, all non-redundant holographic entropy inequalities are superbalanced, i.e. not only do UV divergences cancel in the inequality itself (assuming smooth entangling surfaces), but also in the purification thereof
(13)C NMR investigation of the superconductor MgCNi_3 up to 800K
We report (13)C NMR characterization of the new superconductor MgCNi_3 (He et
al., Nature (411), 54 (2001)). We found that both the uniform spin
susceptibility and the spin fluctuations show a strong enhancement with
decreasing temperature, and saturate below ~50K and ~20K respectively. The
nuclear spin-lattice relaxation rate 1/(13)T_1T exhibits typical behaviour for
isotropic s-wave superconductivity with a coherence peak below Tc=7.0K that
grows with decreasing magnetic field.Comment: Accepted for publication in Physical Review Letter
The Reactivity of MgB2 with Common Substrate and Electronic Materials
The reactivity of MgB2 with powdered forms of common substrate and electronic
materials is reported. Reaction temperatures between 600 C and 800 C,
encompassing the range commonly employed in thin-film fabrication, were
studied. The materials tested for reactivity were ZrO2, yttria stabilized
zirconia (YSZ), MgO, Al2O3, SiO2, SrTiO3, TiN, TaN, AlN, Si, and SiC. At 600 C,
MgB2 reacted only with SiO2 and Si. At 800 C, however, reactions were observed
for MgB2 with Al2O3, SiO2, Si, SiC, and SrTiO3. The Tc of MgB2 decreased in the
reactions with SiC and Al2O3.Comment: 5 figure
A Template for Implementing Fast Lock-free Trees Using HTM
Algorithms that use hardware transactional memory (HTM) must provide a
software-only fallback path to guarantee progress. The design of the fallback
path can have a profound impact on performance. If the fallback path is allowed
to run concurrently with hardware transactions, then hardware transactions must
be instrumented, adding significant overhead. Otherwise, hardware transactions
must wait for any processes on the fallback path, causing concurrency
bottlenecks, or move to the fallback path. We introduce an approach that
combines the best of both worlds. The key idea is to use three execution paths:
an HTM fast path, an HTM middle path, and a software fallback path, such that
the middle path can run concurrently with each of the other two. The fast path
and fallback path do not run concurrently, so the fast path incurs no
instrumentation overhead. Furthermore, fast path transactions can move to the
middle path instead of waiting or moving to the software path. We demonstrate
our approach by producing an accelerated version of the tree update template of
Brown et al., which can be used to implement fast lock-free data structures
based on down-trees. We used the accelerated template to implement two
lock-free trees: a binary search tree (BST), and an (a,b)-tree (a
generalization of a B-tree). Experiments show that, with 72 concurrent
processes, our accelerated (a,b)-tree performs between 4.0x and 4.2x as many
operations per second as an implementation obtained using the original tree
update template
Higgs triplets at like-sign linear colliders and neutrino mixing
We study the phenomenology of the type-II seesaw model at a linear e^-e^-
collider. We show that the process e^-e^- \rightarrow alpha^-beta^- (alpha,
beta = e, mu, tau being charged leptons) mediated by a doubly charged scalar is
very sensitive to the neutrino parameters, in particular the absolute neutrino
mass scale and the Majorana CP-violating phases. We identify the regions in
parameter space in which appreciable collider signatures in the channel with
two like-sign muons in the final state are possible. This includes Higgs
triplet masses beyond the reach of the LHC.Comment: 8 pages, 6 figure
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