Absence of photoemission from the Fermi level in potassium intercalated picene and coronene films: structure, polaron or correlation physics?

The electronic structure of potassium intercalated picene and coronene films has been studied using photoemission spectroscopy. Picene has additionally been intercalated using sodium. Upon alkali metal addition core level as well as valence band photoemission data signal a filling of previously unoccupied states of the two molecular materials due to charge transfer from potassium. In contrast to the observation of superconductivity in K_xpicene and K_xcoronene (x ~ 3), none of the films studied shows emission from the Fermi level, i.e. we find no indication for a metallic ground state. Several reasons for this observation are discussed.Comment: 15 pages, 6 figure

Exciton character in picene molecular solids

We have studied the low-energy electronic excitations of solid picene at 20 K using momentum dependent electron energy-loss spectroscopy. Our results demonstrate the presence of five excitonic features below the transport energy gap of picene, which all are characterized by a negligible dispersion. One of these excitons has not been observed in the optical absorption spectrum of picene molecules in solution and thus is assigned to a (solid-state induced) charge transfer exciton. This conclusion is supported by the momentum dependent intensity variation of this exciton which clearly signals a significant dipole forbidden contribution, in contrast to the other low energy excitations.Comment: 11 pages, 3 figure

Compositional Vector Space Models for Knowledge Base Completion

Knowledge base (KB) completion adds new facts to a KB by making inferences from existing facts, for example by inferring with high likelihood nationality(X,Y) from bornIn(X,Y). Most previous methods infer simple one-hop relational synonyms like this, or use as evidence a multi-hop relational path treated as an atomic feature, like bornIn(X,Z) -> containedIn(Z,Y). This paper presents an approach that reasons about conjunctions of multi-hop relations non-atomically, composing the implications of a path using a recursive neural network (RNN) that takes as inputs vector embeddings of the binary relation in the path. Not only does this allow us to generalize to paths unseen at training time, but also, with a single high-capacity RNN, to predict new relation types not seen when the compositional model was trained (zero-shot learning). We assemble a new dataset of over 52M relational triples, and show that our method improves over a traditional classifier by 11%, and a method leveraging pre-trained embeddings by 7%.Comment: The 53rd Annual Meeting of the Association for Computational Linguistics and The 7th International Joint Conference of the Asian Federation of Natural Language Processing, 201

Does good advice come cheap? On the assessment of risk preferences in the lab and in the field

Advice is important for decision making, especially in the financial sector. We investigate how individuals assess risk preferences of others given sociodemographic information or pictures. Both non-professionals and financial professionals participate in this artefactual field experiment. Subjects mainly rely on the other's self-assessment of risk preferences and on gender when forming the belief about someone else's risk preferences. On average, subjects consider themselves to be more risk-tolerant than the person they evaluate. Subjects use their own risk attitude as a reference point for predicting others' risk preferences. This false consensus effect is less pronounced for young professionals than for senior and non-professionals. Furthermore, financial professionals predict risk preferences more accurately compared to non-professionals

Stereotypes and Risk Attitudes: Evidence from the Lab and the Field

Recent studies have found correlations between risk attitudes and several sociodemographic characteristics. In this paper, we deploy an artefactual fi eld experiment and study whether subjects - non-professionals and financial professionals - are aware of these correlations. This is largely confi rmed by our results for all subject groups. We show that the subjects attach informational value to sociodemographic information when assessing others' risk attitudes. This provides external validity to the correlations found between risk preferences and sociodemographics. A person's self-assessment of risk attitudes is the most helpful device for the subjects' assessments of others, although experienced professionals make use of it to a minor extent than all other subjects

Secure Authentication with Short Re-Usable Passwords

We present Knock Yourself Out (KYO), a password generator that enables secure authentication against a computationally unbounded adversary. Master passwords can be surprisingly short and may be re-used for multiple service accounts even in the event of client compromises and multiple server compromises. At the same time, KYO is transparent to service operators and backwards- compatible. Master passwords are fully client-manageable while secrets shared with service operators can be kept constant. Likewise, secrets can be changed without having to change one’s passwords. KYO does not rely on collision- resistant hash functions and can be implemented with fast non-cryptographic hash functions. We detail the design of KYO and we analyze its security mathematically in a random hash function model. In our empirical evaluation we find that KYO remains secure even if small sets of hash functions are used instead, in other words, KYO requires minimal storage and is highly practical