Simple Amplitudes for \Phi^3 Feynman Ladder Graphs

Recently, we proposed a new approach for calculating Feynman graphs amplitude using the Gaussian representation for propagators which was proven to be exact in the limit of graphs having an infinite number of loops. Regge behavior was also found in a completely new way and the leading Regge trajectory calculated. Here we present symmetry arguments justifying the simple form used for the polynomials in the Feynman parameters $\bar \alpha _{\ell}$, where $\bar \alpha _{\ell}$ is the mean-value for these parameters, appearing in the amplitude for the ladder graphs. (Taking mean-values is equivalent to the Gaussian representation for propagators).Comment: 11 Plain TeX pages, 2 PostScript figures include

A proof of Mader's conjecture on large clique subdivisions in C4C_4-free graphs

Given any integers $s,t\geq 2$, we show there exists some $c=c(s,t)>0$ such that any $K_{s,t}$-free graph with average degree $d$ contains a subdivision of a clique with at least $cd^{\frac{1}{2}\frac{s}{s-1}}$ vertices. In particular, when $s=2$ this resolves in a strong sense the conjecture of Mader in 1999 that every $C_4$-free graph has a subdivision of a clique with order linear in the average degree of the original graph. In general, the widely conjectured asymptotic behaviour of the extremal density of $K_{s,t}$-free graphs suggests our result is tight up to the constant $c(s,t)$.Comment: 25 pages, 1 figur

Spectral properties of transition metal pnictides and chalcogenides: angle-resolved photoemission spectroscopy and dynamical mean field theory

Electronic Coulomb correlations lead to characteristic signatures in the spectroscopy of transition metal pnictides and chalcogenides: quasi-particle renormalizations, lifetime effects or incoherent badly metallic behavior above relatively low coherence temperatures are measures of many-body effects due to local Hubbard and Hund's couplings. We review and compare the results of angle-resolved photoemission spectroscopy experiments (ARPES) and of combined density functional dynamical mean field theory (DFT+DMFT) calculations. We emphasize the doping-dependence of the quasi-particle mass renormalization and coherence properties

Chile Earthquake 2/27/2010: Stories & Lessons

An 8.8 mega-earthquake hit the coast of Chile on February 27th, 2010 and is recorded as one of the largest earthquakes to date. Despite the magnitude of the earthquake, Chile suffered relatively little casualty rates and property damages. To analyze the impact of the earthquake even further, stock trends, bond market fluctuation, government credit ratings and personal anecdotes were factored and compared against other similar mega-earthquake incidents, notably one in Japan on March 11th, 2011 and another in New Zealand on February 22nd, 2011. While Japan and New Zealand both slipped in their government ratings and stock markets following the earthquakes, Chile’s market – both the stock market and the government ratings – have actually increased following the mega-earthquake. Reconstruction spending, low fatality rate, and notably, the country’s deep understanding of earthquake response procedures attributed to the nation’s financial resiliency and quick recovery. Several interviews with government officials, NGO leaders and government officials were conducted to reveal unique leadership characteristics and management techniques applied during the mega-earthquake in order to provide insight beyond numbers

Spanish Economy: Numbers vs Reality

The European economy has been struggling with their debt level since the 2008 financial crisis. Unlike United States whose centralized government play a key role in reverting economic downturns, there is no quantitative easing or definitive centralized authorities in the European Union who can single handily stop the downward economic spiral. To analyze how detrimental the economic conditions are in Europe, personal interviews, data collection and primary research have been conducted to take a deeper dive into how the European economy operates. In addition, the analysis will cover in more depth about how Spain – known for being one of the most fragile economic powerhouses in Europe – has recovered in a much quicker pace, and how its economic figures don’t explain the entire story. Debt levels, corporate indices, macroeconomics and most importantly, culture play a vital role in how Spain is coming back from its heavy economic pressure

Hotels-50K: A Global Hotel Recognition Dataset

Recognizing a hotel from an image of a hotel room is important for human trafficking investigations. Images directly link victims to places and can help verify where victims have been trafficked, and where their traffickers might move them or others in the future. Recognizing the hotel from images is challenging because of low image quality, uncommon camera perspectives, large occlusions (often the victim), and the similarity of objects (e.g., furniture, art, bedding) across different hotel rooms. To support efforts towards this hotel recognition task, we have curated a dataset of over 1 million annotated hotel room images from 50,000 hotels. These images include professionally captured photographs from travel websites and crowd-sourced images from a mobile application, which are more similar to the types of images analyzed in real-world investigations. We present a baseline approach based on a standard network architecture and a collection of data-augmentation approaches tuned to this problem domain

Chemically Ordered Pt–Co–Cu/C as Excellent Electrochemical Catalyst for Oxygen Reduction Reaction

This paper reveals the ordered structure and composition effect to electrochemical catalytic activity towards oxygen reduction reaction (ORR) of ternary metallic Pt–Co–Cu/C catalysts. Bimetallic Pt-Co alloy nanoparticles (NPs) represent an emerging class of electrocatalysts for ORR, but practical applications, e.g. in fuel cells, have been hindered by low catalytic performances owning to crystal phase and atomic composition. Cu is introduced into Pt-Co/C lattices to form PtCoxCu1−x/C (x = 0.25, 0.5 and 0.75) ternary-face-centered tetragonal (fct) ordered ternary metallic NPs. The chemically ordered Pt–Co–Cu/C catalysts exhibit excellent performance of 1.31 A mg−1 Pt in mass activity and 0.59 A cm−2 Pt in specific activity which are significantly higher than Pt-Co/C and commercial Johnson Matthey (JM) Pt/C catalysts, because of the ordered crystal phase and composition control modified the Pt-Pt atoms distance and the surface electronic properties. The presence of Cu improves the surface electronic structure, as well as enhances the stability of catalysts