8,762 research outputs found
Quantum phase transition in the Plaquette lattice with anisotropic spin exchange
I study the influence of anisotropic spin exchange on a quantum phase
transition in the Plaquette lattice driven by the purely quantum effect of
singlet formation. I study the influence of i) a Dzyaloshinskii-Moriya exchange
and ii) four spin exchange on the transition point by evaluating spin--spin
correlations and the spin gap with exact diagonalization. The results point to
a stabilization of the Neel-like long range order when the
Dzyaloshinskii-Moriya exchange is added, whereas the four-spin exchange might
stabilize the singlet order as well as the Neel-like order depending on its
strength.Comment: LaTeX article with 4 pages and 3 figures, prepared with material for
the ICM 200
A phase-field-crystal approach to critical nuclei
We investigate a phase-field-crystal model for homogeneous nucleation.
Instead of solving the time evolution of a density field towards equilibrium we
use a String Method to identify saddle points in phase space. The saddle points
allow to obtain the nucleation barrier and the critical nucleus. The advantage
of using the phase-field-crystal model for this task is its ability to resolve
atomistic effects. The obtained results indicate different properties of the
critical nucleus compared with bulk crystals and show a detailed description of
the nucleation process.Comment: 12 pages, 5 figures, submitte
Relaxation of curvature induced elastic stress by the Asaro-Tiller-Grinfeld instability
A two-dimensional crystal on the surface of a sphere experiences elastic
stress due to the incompatibility of the crystal axes and the curvature. A
common mechanism to relax elastic stress is the Asaro-Tiller-Grinfeld (ATG)
instability. With a combined numerical and analytical approach we demonstrate,
that also curvature induced stress in surface crystals can be relaxed by the
long wave length ATG instability. The numerical results are obtained using a
surface phase-field crystal (PFC) model, from which we determine the
characteristic wave numbers of the ATG instability for various surface
coverages corresponding to different curvature induced compressions. The
results are compared with an analytic expression for the characteristic wave
number, obtained from a continuum approach which accounts for hexagonal
crystals and intrinsic PFC symmetries. We find our numerical results in
accordance with the analytical predictions.Comment: 6 pages, 5 figure
On the Expressivity and Applicability of Model Representation Formalisms
A number of first-order calculi employ an explicit model representation formalism for automated reasoning and for detecting satisfiability. Many of these formalisms can represent infinite Herbrand models. The first-order fragment of monadic, shallow, linear, Horn (MSLH) clauses, is such a formalism used in the approximation refinement calculus. Our first result is a finite model property for MSLH clause sets. Therefore, MSLH clause sets cannot represent models of clause sets with inherently infinite models. Through a translation to tree automata, we further show that this limitation also applies to the linear fragments of implicit generalizations, which is the formalism used in the model-evolution calculus, to atoms with disequality constraints, the formalisms used in the non-redundant clause learning calculus (NRCL), and to atoms with membership constraints, a formalism used for example in decision procedures for algebraic data types. Although these formalisms cannot represent models of clause sets with inherently infinite models, through an additional approximation step they can. This is our second main result. For clause sets including the definition of an equivalence relation with the help of an additional, novel approximation, called reflexive relation splitting, the approximation refinement calculus can automatically show satisfiability through the MSLH clause set formalism
Scalp cooling with adjuvant/neoadjuvant chemotherapy for breast cancer and the risk of scalp metastases: systematic review and meta-analysis.
PurposeThe risk of scalp metastases in patients using scalp cooling for preservation of hair during chemotherapy has been a concern but is poorly described.MethodsA systematic review and meta-analysis of longitudinal studies was undertaken to evaluate the effect of scalp cooling versus no scalp cooling on the risk of scalp metastasis in patients treated for breast cancer with chemotherapy. Electronic databases, journal specific, and hand searches of articles identified were searched. Patients were matched based on disease, treatment, lack of metastatic disease, and sex.ResultsA total of 24 full-text articles were identified for review. Of these articles, ten quantified the incidence of scalp metastasis with scalp cooling over time. For scalp cooling, 1959 patients were evaluated over an estimated mean time frame of 43.1Â months. For no scalp cooling, 1238 patients were evaluated over an estimated mean time frame of 87.4Â months. The incidence rate of scalp metastasis in the scalp cooling group versus the no scalp cooling group was 0.61% (95% CI 0.32-1.1%) versus 0.41% (95% CI 0.13-0.94%); PÂ =Â 0.43.ConclusionThe incidence of scalp metastases was low regardless of scalp cooling. This analysis suggests that scalp cooling does not increase the incidence of scalp metastases
PriPeARL: A Framework for Privacy-Preserving Analytics and Reporting at LinkedIn
Preserving privacy of users is a key requirement of web-scale analytics and
reporting applications, and has witnessed a renewed focus in light of recent
data breaches and new regulations such as GDPR. We focus on the problem of
computing robust, reliable analytics in a privacy-preserving manner, while
satisfying product requirements. We present PriPeARL, a framework for
privacy-preserving analytics and reporting, inspired by differential privacy.
We describe the overall design and architecture, and the key modeling
components, focusing on the unique challenges associated with privacy,
coverage, utility, and consistency. We perform an experimental study in the
context of ads analytics and reporting at LinkedIn, thereby demonstrating the
tradeoffs between privacy and utility needs, and the applicability of
privacy-preserving mechanisms to real-world data. We also highlight the lessons
learned from the production deployment of our system at LinkedIn.Comment: Conference information: ACM International Conference on Information
and Knowledge Management (CIKM 2018
The light CP-even MSSM Higgs mass resummed to fourth logarithmic order
We present the calculation of the light neutral CP-even Higgs mass in the
MSSM for a heavy SUSY spectrum by resumming enhanced terms through fourth
logarithmic order (NLL), keeping terms of leading order in the top Yukawa
coupling , and NNLO in the strong coupling . To this goal,
the three-loop matching coefficient for the quartic Higgs coupling of the SM to
the MSSM is derived to order by comparing the
perturbative EFT to the fixed-order expression for the Higgs mass. The new
matching coefficient is made available through an updated version of the
program Himalaya. Numerical effects of the higher-order resummation are studied
using specific examples, and sources of theoretical uncertainty on this result
are discussed.Comment: 26 pages, 3 figures, matches version published in EPJ
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