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### TG2.2: High energy theory

**I. Coordinator:**

Prof. Yu-tin Huang (National Taiwan University)

yutin@phys.ntu.edu.tw

yutin@phys.ntu.edu.tw

II. Core Members:

II. Core Members:

Prof. Heng-Yu Chen, (National Taiwan University)

Prof. Chong-Sun Chu (National Tsing-Hua University)

Prof. Yu-tin Huang (National Taiwan University)

**III. Research Themes of Core Members**

Here I briey summarize the current research themes of some of the core members:

**Chong-Sun Chu**

Boundary system occurs everywhere in Nature and there are often beautiful phenomena associated with the boundary. For example, the edge modes of topological materials, Casimir forces between conducting plates, Hall eects etc. However boundary system is usually more complicated since the presence of boundary breaks symmetry and so the system with boundary is often richer and display more interesting physics. It is therefore very use- ful to have new approach that allows one to perform powerful analysis of the system that is beyond the standard perturbation approach. Chong-Sun Chu and collaborators have developed and complete the formulation of AdS corre- spondence for boundary CFT (BCFT). Using the AdS/BCFT, he has obtained novel results on boundary Weyl anomaly . He has also looked at boundary energy momentum tensor and uncovered exact relations on Casimir eects in BCFT. These relations can also be proven exactly using eld theory, thus they provide a nontrivial check of the validity of the proposed AdS/BCFT duality. In this project, Chong-SUn plan to further analysis the holographic principle for boundary system.

**Yu-tin Huang**In recent years we have gathered sucient understanding and computation power in bootstrapping CFT correlators and implementing unitarity constraints on higher dimension operators in an eective eld theory. An important arena where these two ideas converge is the string landscape. Any compactied string theory will admit a four-point massless string ampli- tude that is written as a world sheet integral, with its integrand given by a product of free bosons (representing the at space time) and compact 2D CFT (representing the compactied space). The 2D CFT is subject to a 2D bootstrap equations. On the other hand, the resulting string amplitude will have a natural alpha prime (or the compactied scale) expansion that yields the S-matrix for the eective eld theory in four-dimensions, which is subject to the recently developed unitarity bounds. Thus the solution space to both constraints \denes" the allowed string landscape in an on-shell way that is independent of the details of the compactication. In the next two years we aim to initiate preliminary investigation into setting up systematic approach to utilize both constraints. This topic will require much input from the CFT community and can provide model building guidelines that are of phenomenological interest.

**IV. Activities:**

Weekly Strings Seminars: Every Friday 2:20pm at Department of Physics, National Taiwan University; Annual Strings Workshop: Expected to be held in November or earlier, with three to four days duration.

**Brief Justications for the Planned Activities:**

The regular weekly seminars involve both domestic and international speakers, which are essential research activities for theoretical physics. Such occasion allow Thematic Group researchers to exchange current research developments and ideas with international visitors, accelerate the existing and develop th future research projects. Furthermore these regular activities help to increase the visibility of local community, especially for junior people such as students and postdocs.

The annual workshop represents the major event for our Focus group, we usually invite a number of well-known international visitors simultaneously to give sets of pedagogical lectures/seminars on current research topics in theoret- ical high energy physics. The aim is to provide the local researchers, especially junior people necessary introductions to embark research on various latest topics. Moreover, given the number of the excellent Taiwanese junior researchers at early postdoctoral and later PhD levels in theoretical high energy physics, we plan to involve them both as invited speakers, participants and potential organizers in this workshop. This will provide these early stage researchers a relaxing platform to discuss and collaborate with their peers, also benet the local community.

**V**

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**Expected Achievements:**

We expect to continue to successful program in promoting the research from local high energy theory community, especially connect more with other neigh- boring countries such as Japan, South Korea, China and India, as well as newly emerging Thailand. Moreover, given the number of the excellent Taiwanese young researchers in our eld, we expect to plan more activities oriented around their research interests and collaboration needs.