2,417 research outputs found
Decomposition of Lagrangian classes on K3 surfaces
We study the decomposability of a Lagrangian homology class on a K3 surface into a sum of classes represented by special Lagrangian submanifolds, and develop criteria for it in terms of lattice theory. As a result, we prove the decomposability on an arbitrary K3 surface with respect to the KĂ€hler classes in dense subsets of the KĂ€hler cone. Using the same technique, we show that the KĂ€hler classes on a K3 surface which admit a special Lagrangian fibration form a dense subset also. This implies that there are infinitely many special Lagrangian 3-tori in any log Calabi-Yau 3-fold.https://arxiv.org/abs/2001.00202Othe
Effects of electrode surface roughness on motional heating of trapped ions
Electric field noise is a major source of motional heating in trapped ion
quantum computation. While the influence of trap electrode geometries on
electric field noise has been studied in patch potential and surface adsorbate
models, only smooth surfaces are accounted for by current theory. The effects
of roughness, a ubiquitous feature of surface electrodes, are poorly
understood. We investigate its impact on electric field noise by deriving a
rough-surface Green's function and evaluating its effects on adsorbate-surface
binding energies. At cryogenic temperatures, heating rate contributions from
adsorbates are predicted to exhibit an exponential sensitivity to local surface
curvature, leading to either a large net enhancement or suppression over smooth
surfaces. For typical experimental parameters, orders-of-magnitude variations
in total heating rates can occur depending on the spatial distribution of
absorbates. Through careful engineering of electrode surface profiles, our
results suggests that heating rates can be tuned over orders of magnitudes.Comment: 12 pages, 5 figure
Why people adopt VR English language learning systems: An extended perspective of task-technology fit
Virtual Reality (VR) techniques involving immersion, interaction, and imagination, not only can improve conventional teaching methods, but also can enhance the transmission of education training contents through the interaction and simulation characteristics of VR. Incorporating information technology (IT) with English teaching has become an important issue in the academic field. Emerging after computer-assisted teaching, interactive network learning, distance education, and mobile learning in the early days, virtual reality techniques have been regarded as a new trend of merging technology with education. To explore the factors affecting usersâ adoption intention of VR English language learning systems (VRELLS), this study has sought to build a theoretical framework based on the task-technology fit theory (extrinsic motivation) combining usersâ needs (internal and external needs) and satisfaction to put forward an integrated research model (perceived needs-technology fit model), which explicates peopleâs adoption behaviors of VRELLS. An online questionnaire was employed to collect empirical data. A total of 291 samples were analyzed using a structural equation modeling (SEM) approach. The results of the study showed that both perceived needs-technology fit and satisfaction play a significant role in the userâ adoption intention of VRELLS services. In addition, the utilitarian and hedonic needs have a positive impact on the userâs perceived needs-technology fit. Also, it was found that relative advantage, service compatibility and complexity are important factors in influencing individualsâ perceived needs-technology fit. The implications of these findings are discussed along with suggestions for future research
Phantom energy of a quenched, prethermal quantum many-body scar state
Strongly interacting quantum systems can exhibit emergent excitations that
differ qualitatively from their microscopic degrees of freedom. Here we study
an emergent phenomenon that is intrinsic to such systems far from equilibrium:
Namely, the transmutation of attractive interactions into repulsive
interactions. We initialize an attractively interacting Bose gas in a highly
excited and correlated nonthermal state, quench the confining potential, and
measure how the kinetic and total energies evolve after the quench. Although
the bare interactions are attractive, the low-energy degrees of freedom evolve
as if they repel each other: Thus, their kinetic energy paradoxically decreases
as the gas is compressed. We quantify the missing ``phantom'' energy by
benchmarking our experimental results against generalized hydrodynamics (GHD)
calculations. We present evidence that the missing kinetic energy is stored in
very high-momentum modes.Comment: 5 pages, 4 figures with 15-page supplement including 9 figure
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