Symmetry Energy from Holographic QCD

We review the symmetry energy in the context of AdS/CFT correspondence. After constructing $D$ brane configurations corresponding to dense system in boundary theory, we calculate the symmetry energy by solving DBI action of $D$ branes in confining and deconfining phase. We conclude the density dependence of the symmetry energy has scaling law whose power depends only on dimensionality of the branes and space-time.Comment: 9 pages, 5 figures. Some compile errors are corrected. arXiv admin note: substantial text overlap with arXiv:1201.045

Peccei-Quinn invariant singlet extended SUSY with anomalous U(1) gauge symmetry

Recent discovery of the SM-like Higgs boson with $m_h\simeq 125$ GeV motivates an extension of the minimal supersymmetric standard model (MSSM), which involves a singlet Higgs superfield with a sizable Yukawa coupling to the doublet Higgs superfields. We examine such singlet-extended SUSY models with a Peccei-Quinn (PQ) symmetry that originates from an anomalous $U(1)_A$ gauge symmetry. We focus on the specific scheme that the PQ symmetry is spontaneously broken at an intermediate scale $v_{\rm PQ}\sim \sqrt{m_{\rm SUSY}M_{\rm Pl}}$ by an interplay between Planck scale suppressed operators and tachyonic soft scalar mass $m_{\rm SUSY}\sim \sqrt{D_A}$ induced dominantly by the $U(1)_A$ $D$-term, $D_A$. This scheme also results in spontaneous SUSY breaking in the PQ sector, generating the gaugino masses $M_{1/2}\sim \sqrt{D_A}$ when it is transmitted to the MSSM sector by the conventional gauge mediation mechanism. As a result, the MSSM soft parameters in this scheme are induced mostly by the $U(1)_A$ $D$-term and the gauge mediated SUSY breaking from the PQ sector, so that the sparticle masses can be near the present experimental bounds without causing the SUSY flavor problem. The scheme is severely constrained by the condition that a phenomenologically viable form of the low energy operators of the singlet and doublet Higgs superfields is generated by the PQ breaking sector in a way similar to the Kim-Nilles solution of the $\mu$ problem, and the resulting Higgs mass parameters allow the electroweak symmetry breaking with small $\tan\beta$. We find two minimal models with two singlet Higgs superfields, satisfying this condition with a relatively simple form of the PQ breaking sector, and briefly discuss some phenomenological aspects of the model.Comment: 30 pages, 2 tables, references added, version published in JHE

A study of enhanced and interactive online communication service : focusing on e-mail interface

Application of online communication services such as e-mails, e-cards and instant messaging are very useful tools as nonverbal communication for online users. Computer technology has been developing powerful engine tools to be able to convey messages using various methods. Although e-card and instant messenger in online communication services have developed significantly in both visual and functional approaches, it was discovered that e-mail hasn\u27t improved much even though the number of users has significantly increased compared to other services. The purpose of this study is to improve e-mail service both visually and interactively. This research is specifically focused on proposing a new environment for an e-mail program. Incoming and outgoing shows a great interaction between sending and receiving messages based on organized interface and functions. Outgoing is significantly improved and more useful for creating various types of messages. For instance, the user can create messages in terms of different interface environments depending on the formal or informal types of messages. Moreover, the user can classify e-mail into different categories such as personal, business and short memos. There is another consideration with creating kinetic messages in order to make them more personal and unique based on e-card service. In addition, the user can express messages by using kinetic typography based on different typefaces, colors, sounds, and motions. These elements are basic and simple categories in order to be able to create dynamic text messages. The prototype design shows different application tools for online users allowing them to create messages with multiple options. Thus, this research will address potential online communication services in the future

Essays in Asset Pricing and Tail Risk

The first chapter Option Prices in a Model with Stochastic Disaster Risk, co-authored with Jessica Wachter, studies the consistency between the rare disaster mechanism and options data. In contrast to past work based on an iid setup, we find that a model with stochastic disaster risk can explain average implied volatilities well, despite being calibrated to consumption and aggregate market data alone. Furthermore, we extend the stochastic disaster risk model to a two-factor model and show that it can match variation in the level and slope of implied volatilities, as well as the average implied volatility curves. The second chapter Do Rare Events Explain CDX Tranche Spreads?, also co-authored with Jessica Wachter, investigates the rare disaster mechanism based on the data on the CDX index and its tranches. Senior tranches are essentially deep out-of-the-money options because they do not incur any losses until a large number of investment-grade firms default. Using the two-factor stochastic disaster model, we jointly explain the spreads on each CDX tranche, as well as prices on put options and the aggregate market. This paper demonstrates the importance of beliefs about rare disasters and shows a basic consistency in these beliefs across different asset markets. In the third chapter, Correlated Defaults and Economic Catastrophes: Linking the CDS Market and Asset Returns, I consider economic catastrophes as massive correlated defaults and construct a catastrophic tail risk measure from joint default probabilities based on my model as well as information contained in the CDS data. Using the rich information contained in this measure, I find that investors put more weight on future extreme events even after the stock market showed signs of recovery from the recent financial crisis. Furthermore, I show that high catastrophic tail risk robustly predicts high future excess returns for various assets, including stocks, government bonds, and corporate bonds. This risk is negatively priced, generating substantial dispersion in the cross section of stock returns. These results consistently indicate that seemingly impossible economic catastrophes are considered as an important risk source when trading assets

A study on interaction-driven comparison between analog and digital gaming control interface on smartphone

This study aims to find empirical evidence of effectiveness levels: comfort, efficiency, and accuracy between analog and digital interface on smartphone game control through the two different usability tests: 1) A Pilot Study for measuring a correlation contrast with direct and indirect input control from six participants in a small group; 2) A Main Study for finding the effectiveness of “Tap-only affords” basis between a digital and analog input control. The usability test was analyzed by both qualitative and quantitative research methods. There was a total of the 81 participants who were divided into two big groups for comparing one hand and two hands input control, and nine participants per each group implemented a smartphone game based on different input control tasks. The findings appear that direct touch screen interaction is more effective on two hands input control tasks while using an indirect physical input control was more effective on one hand touchscreen