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In this article we prove the existence of a new family of periodic solutions for discrete, nonlinear Schrödinger equations subject to spatially localized driving and damping. They provide an alternate description of the metastable behavior in such lattice systems which agrees with previous predictions for the evolution of metastable states while providing more accurate approximations to these states. We analyze the stability of these breathers, finding a very small positive eigenvalue whose eigenvector lies almost tangent to the surface of the cylinder formed by the family of breathers. This causes solutions to slide along the cylinder without leaving its neighborhood for very long times.
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An orthologous gene coevolution network provides insight into eukaryotic cellular and genomic structure and function
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Semiconducting quantum dots (Q-dots) with strain-tunable electronic properties are good contenders for quantum computing devices, as they hold promise to exhibit a high level of photon entanglement. The optical and electronic properties of Q-dots vary with their size, shape, and makeup. An assortment of Q-dots has been studied, including ZnO, ZnS, CdSe and perovskites [1]. We have employed both Raman spectroscopy (to precisely determine their vibrational frequencies) and UV-VIS spectroscopy (to determine accurately their band gap energies). The electronic band structure and density of states of the ZnO and ZnS Q-dots have been investigated under strain using Density Functional Theory (DFT). The computer program SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) was used to perform the DFT calculations via the linear combination of atomic orbitals (LCAO) method. The spin polarization of such systems may itself be used to encode information or influence the electronic properties of semiconducting Q-dots, which deserve special attention, as they have potential applications in lasers, photovoltaic cells, and imaging. In addition, we have investigated pristine and functionalized graphene nanoplatelets and metal oxides for sensing applications.more » « less
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Abstract One dimension of the emerging politics of connected and automated vehicles (CAVs) is the development of public concerns over their societal implications and associated policy issues. This study uses original survey data from the United States to contribute to the anticipation of future policy and political issues for CAVs. Several studies have surveyed the public regarding CAVs; however, there are few studies that highlight the multidimensional public concerns that CAVs will most likely bring. The study breaks down the concept of “public” by showing that the demographic variables of gender, age, race, ethnicity, income, location (rural, suburban, urban), and political ideology (conservative, moderate, liberal) are significantly associated with three of the most salient public concerns to date (safety, privacy, and data security). Furthermore, the effects of demographic variables also vary across the type of policy issue. For example, women tend to be more concerned about safety than their male counterparts, and Hispanics (Latinx) tend to be more concerned about privacy than non-Hispanics. The research shows how the social scientific analysis of the “politics” of CAVs will require attention to the variegated connections between different types of public concern and different demographic variables.more » « less
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Darmont, J; Novikov, B.; Wrembel, R. (Ed.)Bitcoin [12] is a successful and interesting example of a global scale peer-to-peer cryptocurrency that integrates many techniques and protocols from cryptography, distributed systems, and databases. The main underlying data structure is blockchain, a scalable fully replicated structure that is shared among all participants and guarantees a consistent view of all user transactions by all participants in the system. In a blockchain, nodes agree on their shared states across a large network of untrusted participants. Although originally devised for cryptocurrencies, recent systems exploit its many unique features such as transparency, provenance, fault tolerance, and authenticity to support a wide range of distributed applications. Bitcoin and other cryptocurrencies use permissionless blockchains. In a permissionless blockchain, the network is public, and anyone can participate without a specific identity. Many other distributed applications, such as supply chain management and healthcare, are deployed on permissioned blockchains consisting of a set of known, identified nodes that still might not fully trust each other. This paper illustrates some of the main challenges and opportunities from a database perspective in the many novel and interesting application domains of blockchains. These opportunities are illustrated using various examples from recent research in both permissionless and permissioned blockchains. Two main themes unite the various examples: (1) the important role of distribution and consensus in managing large scale systems and (2) the need to tolerate malicious failures. The advent of cloud computing and large data centers shifted large scale data management infrastructures from centralized databases to distributed systems. One of the main challenges in designing distributed systems is the need for fault-tolerance. Cloud-based systems typically assume trusted infrastructures, since data centers are owned by the enterprises managing the data, and hence the design typically only assumes and tolerates crash failures. The advent of blockchain and the underlying premise that copies of the blockchain are distributed among untrusted entities has shifted the focus of fault-tolerance from tolerating crash failures to tolerating malicious failures. These interesting and challenging settings pose great opportunities for database researchers.more » « less
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A function f∶{0,1}n→ {0,1} is called an approximate AND-homomorphism if choosing x,y∈n uniformly at random, we have that f(x∧ y) = f(x)∧ f(y) with probability at least 1−ε, where x∧ y = (x1∧ y1,…,xn∧ yn). We prove that if f∶ {0,1}n → {0,1} is an approximate AND-homomorphism, then f is δ-close to either a constant function or an AND function, where δ(ε) → 0 as ε→ 0. This improves on a result of Nehama, who proved a similar statement in which δ depends on n. Our theorem implies a strong result on judgement aggregation in computational social choice. In the language of social choice, our result shows that if f is ε-close to satisfying judgement aggregation, then it is δ(ε)-close to an oligarchy (the name for the AND function in social choice theory). This improves on Nehama’s result, in which δ decays polynomially with n. Our result follows from a more general one, in which we characterize approximate solutions to the eigenvalue equation f = λ g, where is the downwards noise operator f(x) = y[f(x ∧ y)], f is [0,1]-valued, and g is {0,1}-valued. We identify all exact solutions to this equation, and show that any approximate solution in which f and λ g are close is close to an exact solution.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/sciadv.abn0105
