Giant Magnons and Spiky Strings on S^3 with B-field

We study solutions for a rotating string on S^3 with a background NS-NS B-field and show the existence of spiky string and giant magnon as two limiting solutions. We make a connection to the sine-Gordon model via the Polyakov worldsheet action and study the effect of B-field. In particular, we find the magnon solution can be mapped to the excitation of a fractional spin chain. We conjecture a B-deformed SYM to be the gauge theory dual to this background.Comment: 22 pages, 3 figures, more references adde

Correlated Phases of Population Imbalanced Fermi-Fermi Mixtures on an Optical Lattice

We study a two species fermion mixture with different populations on a square lattice modeled by a Hubbard Hamiltonian with on-site inter-species repulsive interaction. Such a model can be realized in a cold atom system with fermionic atoms in two different hyperfine states loaded on an optical lattice and with tunable inter-species interaction strength via external fields. For a two-dimensional square lattice, when at least one of the fermion species is close to half-filling, the system is highly affected by lattice effects. With the majority species near half-filling and varying densities for the minority species, we find that several correlated phases emerge as the ground state, including a spin density wave state, a charge density wave state with stripe structure, and various p-wave BCS pairing states for both species. We study this system using a functional renormalization group method, determine its phase diagram at weak coupling, discuss the origin and characteristics of each phase, and provide estimates for the critical temperatures.Comment: 5 pages, 4 figures, figures update

Unconventional superconducting phases on a two-dimensional extended Hubbard model

We study the phase diagram of the extended Hubbard model on a two-dimensional square lattice, including on-site (U) and nearest-neighbor (V) interactions, at weak couplings. We show that the charge-density-wave phase that is known to occur at half-filling when 4V > U gives way to a d_{xy} -wave superconducting instability away from half-filling, when the Fermi surface is not perfectly nested, and for sufficiently large repulsive and a range of on-site repulsive interaction. In addition, when nesting is further suppressed and in presence of a nearest-neighbor attraction, a triplet time-reversal breaking (p_x + ip_y)-wave pairing instability emerges, competing with the d_{x2+y2} pairing state that is known to dominate at fillings just slightly away from half. At even smaller fillings, where the Fermi surface no longer presents any nesting, the (p_x +ip_y)-wave superconducting phase dominates in the whole regime of on-site repulsions and nearest-neighbor attractions, while d_{xy}-pairing occurs in the presence of on-site attraction. Our results suggest that zero-energy Majorana fermions can be realized on a square lattice in the presence of a magnetic field. For a system of cold fermionic atoms on a two-dimensional square optical lattice, both an on-site repulsion and a nearest-neighbor attraction would be required, in addition to rotation of the system to create vortices. We discuss possible ways of experimentally engineering the required interaction terms in a cold atom system

d_{xy}-Density wave in fermion-fermion cold atom mixtures

We study density wave instabilities in a doubly-degenerate Fermi-Fermi mixture with $SU(2)\times SU(2)$ symmetry on a square lattice. For sufficiently large on-site inter-species repulsion, when the two species of fermions are both at half-filling, two conventional ($s$-wave) number density waves are formed with a $\pi$-phase difference between them to minimize the inter-species repulsion. Upon moving one species away from half-filling, an unconventional density wave with $d_{xy}$-wave symmetry emerges. When both species are away from the vicinity of half-filling, superconducting instabilities dominate. We present results of a functional renormalization-group calculation that maps out the phase diagram at weak couplings. Also, we provide a simple explanation for the emergence of the $d_{xy}$-density wave phase based on a four-patch model. We find a robust and general mechanism for $d_{xy}$-density-wave formation that is related to the shape and size of the Fermi surfaces. The density imbalance between the two species of fermions in the vicinity of half-filling leads to phase-space discrepancy for different inter-species Umklapp couplings. Using a phase space argument for leading corrections in the one-loop renormalization group approach to fermions, we show that the phase-space discrepancy in our system causes opposite flows for the two leading intra-species Umklapp couplings and that this triggers the $d_{xy}$-density-wave instability.Comment: revised long version; 8 pages, 7 figure

Effect of Age on Allergen Responses of Allergic Patients in Southern Taiwan

To survey airborne and food allergen patterns in southern Taiwan and to analyze the effect of age on response to different allergens, we tested samples from 4,411 allergic patients at Kaohsiung Medical University Hospital using the MAST-CLA test (new Taiwan panel). A total of 2,212 (50.1%) samples showed a positive response. We grouped allergic patients into five age groups. Milk and egg white were the main food allergens in the younger groups (< 3 years old and 3-6 years old). Shrimp, crab, and shellfish were the main allergens in the groups aged 7-12, 13-18, and more than 18 years. Among airborne allergens, house dust and mites Dermatophagoides farinae and D. pteronyssinus were the main allergens in all age groups, whereas the frequency of response to cockroach allergen was low in the group aged less than 3 years, but increased in the other age groups. There was a sharp increase in the frequency of response to airborne allergens after 3 years old and a sharp decrease in response to food allergens. Among subjects allergic to both airborne and food allergens, there was a positive MAST-CLA rate of 19.9% to 26% (all five age groups, no significant difference). When we compared our results with those from Taipei Veterans General Hospital in northern Taiwan, there were significant differences for yeast, peanut, feather mix, dog dander, cockroach, D. farinae and D. pteronyssinus allergens (p < 0.01). These differences were probably caused by differences in patient location, patient age, disease patterns and allergen panels

Using Hidden Markov Model for Stock Day Trade Forecasting

Around the world, the Hidden Markov Models (HMM) are the most popular methods in the machine learning and statistics for modeling sequences, especially in speech recognition domain. According to the number of patent applications for speech recognition technology form 1988 to 1998, the trend shows that this method has become very mature. In this thesis, we will make a new use of the HMM and apply it on day trading stock forecast. However, the HMM is based on probability and statistics theory. In a statistics framework, the HMM is a composition of two stochastic processes, a Hidden Markov chain, which accounts for temporal variability, and an observable process, which accounts for spectral variability. The combination contains uncertainly status just likes the stock walk trace. Therefore, the HMM and the stock walk trace have the same idea by coincidence. In this thesis, we will try to learn the stock syntax; just like how the HMM model was used in speech recognition in different languages, and the take the next step ahead in price prediction. Additionally, the stock market is the reflection of the economy. The stock trace is impacted by many factors such as policy, psychology, microeconomics, economics, and capital, etc. There, in this thesis, the TAIFEX Taiwan index futures (TX) and day trade are used to avoid all the uncertainty factors. After the all experiments, it is proven that the HMM is better than the benchmark methodRandom Walk method and the Investment Trust & Consulting Association method- Modified Trading method. Moreover, the result is very conspicuous by the statistics testing of significance

The Key Success Factors of Wearable Computing Devices: An User-Centricity Perspective

In modern electronic business era, the currently popular topic of wearable computing devices (WCD) has prompted foreign and local industry players to look proactively into various WCD-related developments, including the external appearances of WCD hardware, software applications, human-device interface designs, and the appearances of WCDs expected by general users. Setting aside the necessary functional specifications and application requirements of WCDs, the wearing habits that general users have already developed is a more fundamental consideration. These habits should form the basis for the design of both WCD hardware and software at the technological level. In this paper, an analysis is made of the items that general users customarily wear and the purpose(s) and frequency of wearing them. The findings will serve as a reference for industry players who wish to enter the WCD market

Design of a Multi-Host Shared Memory Services System

Memory cache is one kind of memory, through which data and objects are stored, thereby reducing the time required to access the database and hard disk I/O, and achieving accelerated technology effects by a significant application in large-scale web systems. In this paper, we design Memcahed Helper (MH), based on a set of memcached with the scalability of a distributed memory cache system, in line with the progress of the cloud environment. The experimental results show that this system and the more efficient use of memory, provides better performance and speed