Spectral Decomposition of Missing Transverse Energy at Hadron Colliders

We propose a spectral decomposition to systematically extract information of dark matter at hadron colliders. The differential cross section of events with missing transverse energy (MET) can be expressed by a linear combination of basis functions. In the case of $s$-channel mediator models for dark matter particle production, basis functions are identified with the differential cross sections of sub-processes of virtual mediator and visible particle production while the coefficients of basis functions correspond to dark matter invariant mass distribution in the manner of the K\"all\'en-Lehmann spectral decomposition. For a given MET data set and mediator model, we show that one can differentiate a certain dark matter-mediator interaction from another through spectral decomposition.Comment: 6+4 pages, 6 figures, PRL versio

Regularity estimates for singular parabolic measure data problems with sharp growth

We prove global gradient estimates for parabolic $p$-Laplace type equations with measure data, whose model is $$u_t - \textrm{div} \left(|Du|^{p-2} Du\right) = \mu \quad \textrm{in} \ \Omega \times (0,T) \subset \mathbb{R}^n \times \mathbb{R},$$ where $\mu$ is a signed Radon measure with finite total mass. We consider the singular case $$\frac{2n}{n+1} <p \le 2-\frac{1}{n+1}$$ and give possibly minimal conditions on the nonlinearity and the boundary of $\Omega$, which guarantee the regularity results for such measure data problems.Comment: 28 page

Click-aware purchase prediction with push at the top

Eliciting user preferences from purchase records for performing purchase prediction is challenging because negative feedback is not explicitly observed, and because treating all non-purchased items equally as negative feedback is unrealistic. Therefore, in this study, we present a framework that leverages the past click records of users to compensate for the missing user-item interactions of purchase records, i.e., non-purchased items. We begin by formulating various model assumptions, each one assuming a different order of user preferences among purchased, clicked-but-not-purchased, and non-clicked items, to study the usefulness of leveraging click records. We implement the model assumptions using the Bayesian personalized ranking model, which maximizes the area under the curve for bipartite ranking. However, we argue that using click records for bipartite ranking needs a meticulously designed model because of the relative unreliableness of click records compared with that of purchase records. Therefore, we ultimately propose a novel learning-to-rank method, called P3Stop, for performing purchase prediction. The proposed model is customized to be robust to relatively unreliable click records by particularly focusing on the accuracy of top-ranked items. Experimental results on two real-world e-commerce datasets demonstrate that P3STop considerably outperforms the state-of-the-art implicit-feedback-based recommendation methods, especially for top-ranked items.Comment: For the final published journal version, see https://doi.org/10.1016/j.ins.2020.02.06

Art therapy with Korean migrant women in a Korean community in the UK

This thesis addresses an art therapy intervention in a Korean community in the UK. It describes the historical, social and cultural contexts of South and North Koreans, including Korean art and education throughout history in order to contextualize the research and the findings. It also portrays the researcher’s experiences as a Korean migrant as well as an art psychotherapist, exposed first to Eastern culture then to Western, becoming an art therapist and then working with Korean migrants in the UK. Case material from an art therapy group, an art activity group and individual art therapy with Korean migrants in different organisations were analysed alongside the author’s autobiographical journey which was also considered as a ‘case’. This research therefore explores how art therapy might be applicable to Korean migrants who are living in a Korean community in the UK in the context of the cultural complexities and social change characterised by migration. Throughout the research a qualitative research design was used which analysed the cases with an ethnographical lens, based on existing migration theories. Five conceptualisations were discovered that enable this researcher to understand this particular social group of Korean migrants. These are: cultural transition, or not; the relationship between migration experience and mental health; the influence of religion on migrants’ mental health; the relationship between Korean art education and art therapy; and the influence of socio-political issues in the Korean migrants’ community. These theoretical lenses illuminated how the process of migration has a massive impact on the migrants’ life in the host country and showed how it interweaves with the historical, social and cultural context of Korea. Many assumptions were challenged during the research. Particular considerations for working with Korean people in art therapy were explored, and the research concluded that it was important to be aware and work appropriately with people of other cultures in art therapy within the Western framework, to maintain its relationship between art, health and culture. This study has implications for the significance of examining the art therapist’s assumptions and presuppositions when art therapy is introduced to another culture, and when working with similarity and difference. It also has implications for art therapy practice, namely the importance of considering: the cultural values of clients’ origins, including their previous experiences of art-making and art education, despite migrants’ exposure to Western society; the current socio-cultural context of clients’ lives in their community in the host country; and adjusting art therapy practice so that it is appropriate to clients from different cultures

Dynamical mean-field theory of Hubbard-Holstein model at half-filling: Zero temperature metal-insulator and insulator-insulator transitions

We study the Hubbard-Holstein model, which includes both the electron-electron and electron-phonon interactions characterized by $U$ and $g$, respectively, employing the dynamical mean-field theory combined with Wilson's numerical renormalization group technique. A zero temperature phase diagram of metal-insulator and insulator-insulator transitions at half-filling is mapped out which exhibits the interplay between $U$ and $g$. As $U$ ($g$) is increased, a metal to Mott-Hubbard insulator (bipolaron insulator) transition occurs, and the two insulating states are distinct and can not be adiabatically connected. The nature of and transitions between the three states are discussed.Comment: 5 pages, 4 figures. Submitted to Physical Review Letter