113398368
Calabi-Yau Manifolds, Hermitian Yang-Mills Instantons, and Mirror Symmetry
We address the issue of why Calabi-Yau manifolds exist with a mirror pair. We observe that the irreducible spinor representation of the Lorentz group requires us to consider the vector spaces of two forms and four forms on an equal footing. The doubling of the two-form vector space due to the Hodge duality doubles the variety of six-dimensional spin manifolds. We explore how the doubling is related to the mirror symmetry of Calabi-Yau manifolds. Via the gauge theory formulation of six-dimensional Riemannian manifolds, we show that the curvature tensor of a Calabi-Yau manifold satisfies the Hermitian Yang-Mills equations on the Calabi-Yau manifold. Therefore, the mirror symmetry of Calabi-Yau manifolds can be recast as the mirror pair of Hermitian Yang-Mills instantons. We discuss the mirror symmetry from the gauge theory perspective.
11614231
Moduli flow and non-supersymmetric AdS attractors
We investigate the attractor mechanism in gauged supergravity in the presence of higher derivative terms. In particular, we discuss the attractor behavior of static black hole horizons in anti-de Sitter spacetime by using the effective potential approach as well as Sen's entropy function formalism. We use the holographic techniques to interpret the moduli flow as an RG flow towards the IR attractor horizon. We find that the holographic c-function obeys the expected properties and point out some subtleties in understanding attractors in AdS.
118481681
Thermal aspects of the ABJM theory: currents and condensations
To study thermal aspects of the ABJM theory in the strongly coupled regime, we carry out the invariant dimensional reduction of the type IIA supergravity down to four dimensions. We then investigate zero and finite temperature responses of the operators which are dual to the AdS scalar and vector fields. Two scalar operators are shown to have finite-temperature condensations by coupling of the constant source term. The currents dual to the massless and massive gauge fields are not induced by coupling of the constant boundary vector potential, which implies that the phase described by the black brane background is not superconducting. We also discuss a generalization to charged (dyonic) black holes.
117135154
Toroidal AdS Charged Branes and Toda Equations
In this note, we consider the equations of motion for charged branes in AdS space and show that they can be cast into one-dimensional coupled Toda type. Then we solve the equations of motion to construct static charged AdS brane solutions which are invariant under translation along $p$ directions and have toroidal symmetry. The solutions are described by mass, charges and a dilaton coupling constant.
118510404
Symmetry Breaking Phase Transitions in ABJM Theory with a Finite U(1) Chemical Potential
We consider the U(1) charged sector of ABJM theory at finite temperature, which corresponds to the Reissner-Nordstrom AdS black hole in the dual type IIA supergravity description. Including back-reaction to the bulk geometry, we show that phase transitions occur to a broken phase where SU(4) R-symmetry of the field theory is broken spontaneously by the condensation of dimension one or two operators. We construct the composite operators out of fields in ABJM theory and describe the phase transition with the dual gravity solutions. We show numerically and analytically that the relevant critical exponents for the dimension one operator agree precisely with those of mean field theory in the strongly coupled regime of the large N planar limit.
16002558
Higher derivative correction to Kaluza–Klein black hole solution
We investigate the attractor mechanism in a Kaluza–Klein black hole solution in the presence of higher derivative terms. In particular, we discuss the attractor behavior of static black holes by using the effective potential approach as well as the entropy function formalism. We consider different higher derivative terms with a general coupling to the moduli field. For the R2 theory, we use an effective potential approach, looking for solutions which are analytic near the horizon and showing that they exist and enjoy attractor behavior. The attractor point is determined by extremization of the modified effective potential at the horizon. We study the effect of the general higher derivative corrections of Rn terms. Using the entropy function we define the modified effective potential and we find the conditions to have the attractor solution. In particular for a single charged Kaluza–Klein black hole solution we show that a higher derivative correction dresses the singularity for an appropriate coupling, and we can find the attractor solution.
8187163
Proton beam energy measurement using semiconductor detectors at the 45MeV test beam line of PEFP
For the pilot and feasibility studies on the development of beam utilization technologies of PEFP (proton engineering frontier project), the test beam line was installed at the MC-50 cyclotron of KIRAMS (Korea institute of radiological and medical sciences) [1-2]. The energy measurement of proton beam with high accuracy is very important for the some experiments such as radiation hardness test of semiconductor devices for the spacecraft, detector development and test for the nuclear physics, etc. Energy measurement of 35 MeV and 45 MeV proton beam using a 5 mm thick Si(Li) in air was performed. The energy was controlled by Al degrader in the range of 0.02 mm~6.2 mm. The measured value was compared to the results of code simulation using SRIM 2003.
55648402
Beam Commissioning of KOMAC Linac
The KOMAC (Korea multi-purpose accelerator complex), whose first phase is the proton engineering frontier project, developed a 100-MeV proton linac which consists of a 50 keV injector, a 3-MeV radio frequency quadrupole (RFQ) and a 100-MeV drift tube linac (DTL). The installation of the linac was finished and in commissioning stage. The goal of the beam commissioning in June 2013 is accelerating 100-MeV proton beams with the beam power of 1 kW to the beam dump which is located downstream of the linac. This work summarized the present status and plan of the beam commissioning of the linac.
113201344
Design of Machine Protection System for the PEFP 100MeV Linac
37852911
Design of 100 MeV Proton Beam Irradiation Facility for the PEFP 100 MeV Linac
The Proton Engineering Frontier Project (PEFP) will install a 100-MeV proton linear accelerator at Gyeong-ju site. For the beam commissioning of 100 MeV proton linac, the two target rooms (TR 103, TR 23) will be prepared as a starter among 10 target room. To design the irradiation equipment in TR 103, we have investigated general propagation shape and spatial distribution of proton beam, when 100 MeV proton beam extracted from vacuum in the beam lines through beam window by Monte carlo method. On the basis of this result, we have designed beam irradiation components and their configuration. The beam irradiation facility consist of beam window, beam dump, support frame, sample support and beam current monitor. To minimize residual radioactivity induced by incident proton beam, the pure aluminum was selected as the material of beam dump and the aluminum alloy was selected as material of other irradiation equipment. This residual radioactivity of equipment was estimated by Monte carlo method. In this paper, the details of this irradiation equipment design are presented.
140083239
BEAM TESTS OF THE PEFP 20 MEV ACCELERATOR *
Proton Engineering Frontier Project (PEFP) 20MeV proton accelerator has been installed and tested at KAERI (Korea Atomic Energy Research Institute) site. After the radiation license was issued, some parts were modified to increase a peak beam current above 1mA. A proton injector composed of an ion source and a LEBT (Low Energy Beam Transport) was modified for better transmission rate through the LEBT. The field profile of the RFQ was measured to check the dipole field effect. In addition, beam loss was measured along the DTL to check and adjust the operating parameters. In this paper, the modifications of the 20MeV accelerator are summarized and the recent test results are presented.