1,578 research outputs found
Instanton Calculus and Nonperturbative Relations in N=2 Supersymmetric Gauge Theories
Using instanton calculus we check, in the weak coupling region, the
nonperturbative relation =i\pi\left(\cf-{a\over 2}
{\partial\cf\over\partial a}\right) obtained for a N=2 globally
supersymmetric gauge theory. Our computations are performed for instantons of
winding number k, up to k=2 and turn out to agree with previous nonperturbative
results.Comment: 18 pages, latex file, no figure
Diagrammatic Quantum Monte Carlo for Two-Body Problem: Exciton
We present a novel method for precise numerical solution of the irreducible
two-body problem and apply it to excitons in solids. The approach is based on
the Monte Carlo simulation of the two-body Green function specified by
Feynman's diagrammatic expansion. Our method does not rely on the specific form
of the electron and hole dispersion laws and is valid for any attractive
electron-hole potential. We establish limits of validity of the Wannier (large
radius) and Frenkel (small radius) approximations, present accurate data for
the intermediate radius excitons, and give evidence for the charge transfer
nature of the monopolar exciton in mixed valence materials.Comment: 4 pages, 5 figure
Eikonal phase matrix, deflection angle, and time delay in effective field theories of gravity
The eikonal approximation is an ideal tool to extract classical observables
in gauge theory and gravity directly from scattering amplitudes. Here we
consider effective theories of gravity where in addition to the
Einstein-Hilbert term we include non-minimal couplings of the type ,
and . In particular, we study the scattering of gravitons and photons of
frequency off heavy scalars of mass in the limit , where is the momentum transfer. The presence of
non-minimal couplings induces helicity-flip processes which survive the eikonal
limit, thereby promoting the eikonal phase to an eikonal phase matrix. We
obtain the latter from the relevant two-to-two helicity amplitudes that we
compute up to one-loop order, and confirm that the leading-order terms in
exponentiate \`{a} la Amati, Ciafaloni and Veneziano. From the
eigenvalues of the eikonal phase matrix we then extract two physical
observables, to 2PM order: the classical deflection angle and Shapiro time
delay/advance. Whenever the classical expectation of helicity conservation of
the massless scattered particle is violated, i.e. the eigenvalues of the
eikonal matrix are non-degenerate, causality violation due to time advance is a
generic possibility for small impact parameter. We show that for graviton
scattering in the and theories, time advance is circumvented if the
couplings of these interactions satisfy certain positivity conditions, while it
is unavoidable for graviton scattering in the theory and photon
scattering in the theory. The scattering processes we consider mimic the
deflection of photons and gravitons off spinless heavy objects such as
black~holes.Comment: 38 pages. v2: published version, small typos corrected, reference
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A multi-channel trigger and acquisition board for TDC-based readout: Application to the cosmic rays detector of the PolarQuEEEst 2018 project
In the summer of 2018, the PolarQuEEEst experiment accomplished a measurement of cosmic rays flux in the Arctic. The detector, installed on a sailboat, was based on scintillation tiles read by a total of 16 SiPM. A multi-channel board (called TRB) has been designed to process the discriminated SiPM signals providing both self-trigger capability and time-to-digital conversion; it was based on a Cyclone-V Intel FPGA. Time-to-digital conversion has been implemented both into FPGA and with the HPTDC chip (as a backup). In this document the board will be described, enlightening the main features and the achieved performance. Lastly, the PolarQuEEEst measurement campaigns will be briefly described, showing how the TRB board has proved to be effective for experiments which require low power consumption, integration with position and environmental sensors and great portability as well. Final thoughts on future improvements will be also discussed
Electron self-trapping in intermediate-valent SmB6
SmB6 exhibits intermediate valence in the ground state and unusual behaviour
at low temperatures. The resistivity and the Hall effect cannot be explained
either by conventional sf-hybridization or by hopping transport in an impurity
band. At least three different energy scales determine three temperature
regimes of electron transport in this system. We consider the ground state
properties, the soft valence fluctuations and the spectrum of band carriers in
n-doped SmB6. The behaviour of excess conduction electrons in the presence of
soft valence fluctuations and the origin of the three energy scales in the
spectrum of elementary excitations is discussed. The carriers which determine
the low-temperature transport in this system are self-trapped electron-polaron
complexes rather than simply electrons in an impurity band. The mechanism of
electron trapping is the interaction with soft valence fluctuations.Comment: 12 pages, 3 figure
Instanton Calculus and SUSY Gauge Theories on ALE Manifolds
We study instanton effects along the Coulomb branch of an N=2 supersymmetric
Yang-Mills theory with gauge group SU(2) on Asymptotically Locally Euclidean
(ALE) spaces. We focus our attention on an Eguchi-Hanson gravitational
background and on gauge field configurations of lowest Chern class.Comment: 15 pages, LaTeX file. Extended version to be published in Physical
Review
Heterogeneous validity of daily data on symptoms of seasonal allergic rhinitis recorded by patients using the e-diary AllergyMonitor®
Background: Patient-generated symptom and medication scores are essential for diagnostic and therapeutic decisions in seasonal allergic rhinitis (SAR). Previous studies have shown solid consistencies between different scores at population level in real-life data and trials. For clinicians, the evaluation of individual data quality over time is essential to decide whether to rely on these data in clinical decision-making.
Objective: To analyze the consistency of different symptom (SS) and symptom medication scores (SMSs) at individual level in two study cohorts with different characteristics and explore individual patient trajectories over time.
Methods: Within the pilot phase of the @IT.2020 project on diagnostic synergy of mobile health and molecular IgE assessment in patients with SAR, we analyzed data of 101 children and 93 adults with SAR and instructed them to record their symptoms and medication intake daily via the mobile app AllergyMonitor®. We then assessed the correlation between different SMS and a visual analogue scale (VAS) on the impact of allergy symptoms on daily life at population and individual level.
Results: At population level, the Rhinoconjunctivitis total symptom score (RTSS) correlated better with VAS than the combined symptom and medication score (CSMS). At individual level, consistency among RTSS and VAS was highly heterogeneous and unrelated to disease severity or adherence to recording. Similar heterogeneity was observed for CSMS and VAS.
Conclusions: The correlation of clinical information provided by different disease severity scores based on data collected via electronic diaries (e-diaries), is sufficient at population level, but broadly heterogeneous for individual patients. Consistency of the recorded data must be examined for each patient before remotely collected information is used for clinical decision making
On super form factors of half-BPS operators in N=4 super Yang-Mills
Open Access, (c) The Authors. Article funded by SCOAP3. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited
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