A Numerical Study of Gluon Scattering Amplitudes in N=4 Super Yang-Mills Theory at Strong Coupling

We study gluon scattering amplitudes in N=4 super Yang-Mills theory at strong coupling via the AdS/CFT correspondence. We solve numerically the discretized Euler-Lagrange equations on the square worldsheet for the minimal surface with light-like boundaries in AdS spacetime. We evaluate the area of the surface for the 4, 6 and 8-point amplitudes using worldsheet and radial cut-off regularizations. Their infrared singularities in the cut-off regularization are found to agree with the analytical results near the cusp less than 5% at 520x520 lattice points.Comment: Latex, 23 pages, 19 figure

Impurity Non-Preserving 3-Point Correlators of BMN Operators from PP-Wave Holography II : Fermionic Excitations

The holographic principle in the pp-wave limit proposed in our previous works is further confirmed by studying impurity non-preserving processes which contain a fermionic BMN operator with one scalar and one fermion impurities. We show that the previously proposed duality relation between the matrix elements of the three point interaction Hamiltonian in the holographic string field theory and the OPE coefficients in super Yang-Mills theory holds to the leading order in the large $\mu$ limit. Operator mixing is required to obtain the BMN operator of definite conformal dimension which corresponds to the string state with one scalar and one fermion excitations. The mixing term plays a crucial role for our duality relation to be valid. Our results, combined with those in the previous papers, provide a positive support that our duality relation holds for the general process regardless of the kind of impurities and of whether impurities conserve or not.Comment: 44 pages, 6 figure

Resolving the Holography in the Plane-Wave Limit of AdS/CFT Correspondence

The issue of holographic mapping between bulk and boundary in the plane-wave limit of AdS/SYM correspondence is reexamined from the viewpoint of correlation functions. We first study the limit of large angular momentum for the so-called GKP-W relation in supergeravity approximation, connecting directly the effective action in the bulk and the generating functional of correlation functions on the boundary. The spacetime tunneling picture which has been proposed in our previous works naturally emerges. This gives not only a justification of our previous proposal, with some important refinements, on the mapping between bulk effective interaction and the CFT coefficients on the boundary in the plane-wave limit, but also implies various insights on the interpretation of holography in the plane-wave limit. Based on this result, we construct a new `holographic' string field theory. We confirm for several nontrivial examples that this gives the CFT coefficients derived by perturbation theory on the gauge-theory side. Our results are useful for understanding how apparently different duality maps proposed from different standpoints are consistent with each other and with our definite spacetime picture for the AdS holography in the plane-wave limit.Comment: corrected typos, 57 page

局所型前立腺癌に対する3次元原体照射後の晩期消化管障害に関連する臨床因子

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Effects of image lag on real-time target tracking in radiotherapy

There is a concern that image lag may reduce accuracy of real-time target tracking in radiotherapy. This study was performed to investigate influence of image lag on the accuracy of target tracking in radiotherapy. Fluoroscopic image: were obtained using a direct type of dynamic flat-panel detector (FPD) system under conditions of target tracking during radiotherapy. The images continued to be read out after X-irradiations and cutoff, and image lag properties in the system were then determined. Subsequently, a tungsten materials plate with a precision edge was mounted on to a motor control device, which provided a constant velocity. The plate was moved into the center of the detector at movement rate of 1 and 20 mm/s, covering lung tumor movement of normal breathing, and MTF and profile curves were measured on the edges covering and uncovering the detector. A lung tumor with blurred edge due to image lag was simulated using the results and then superimposed on breathing chest radiographs of a patient. The moving target with and without image lag was traced using a template-matching technique. In the results, the target could be traced within a margin for error ii external radiotherapy. The results indicated that there was no effect of image lag on target tracking in usual breathing speed in a radiotherapy situation. Further studies are required to investigate influence by the other factors, such a: exposure dose, target size and shape, imaging rate, and thickness of a patient\u27s body. © 2010 SPIE

Comments on gluon 6-point scattering amplitudes in N=4 SYM at strong coupling

We use the AdS/CFT prescription of Alday and Maldacena \cite{am} to analyze gluon 6-point scattering amplitudes at strong coupling in ${\cal N}=4$ SYM. By cutting and gluing we obtain AdS 6-point amplitudes that contain extra boundary conditions and come close to matching the field theory results. We interpret them as parts of the field theory amplitudes, containing only certain diagrams. We also analyze the collinear limits of 6- and 5-point amplitudes and discuss the results.Comment: 35 pages, 7 figures, latex, references adde

Four-Dimensional Carbon Ion Dose Assessment in Respiratory-Gated Lung Therapy: Simulation Study in Respiratory Pattern Variation Cases

Purpose: To estimate the effects of the irregular respiratory pattern during the carbon-beam treatment of lung cancer in the four-dimensional treatment planning, we simulated the irregular respiratory motion by the NCAT phantom and calculated the accumulated dose for respiratory gated and ungated treatment. Method and Materials: 4D NCAT phantom was used to simulate the irregular respiratory tumor motion during several cycles of respiration. The treatment planning was performed based on the first cycle of the respiration. The cycle was subdivided into 10 phases and the prescribed dose was distributed so that all points in the planning target volume (PTV) receives more than 90 percent of the total prescribed dose. The total of 52.8 GyE was delivered from four beam ports with angles selected to be 340, 70, 20, and 110 degrees. The plan was scheduled both for ungated and gated treatment. For the respiratory-gated treatment, the gating window was set in T40%–T60% phases. The dose calculation was based on the pencil beam algorithm. The accumulated dose was evaluated and compared between gated- and ungated- results in terms of V20, D95 and dose-volume histogram (DVH). Results: For the ungated case the dose conformation was deteriorated compared to the ideal case where the respiratory pattern was completely the same as in the treatment planning, while, for the gated treatment, the improved dose conformation was observed in terms of both D95 and V20. Conclusion: Though the 4D planning is effective to estimate internal margin, the irregular respiratory pattern may deteriorate the conformation of the accumulated dose during the whole treatment. The gating treatment, if appropriately synchronized, is effective both for the dose conformity and the reduction of the extra dose to the normal tissues or organs at risks.51st AAPM Annual Meetin

Evaluation of respiratory pattern during respiratory-gated radiotherapy.

The respiratory cycle is not strictly regular, and generally varies in amplitude and period from one cycle to the next. We evaluated the characteristics of respiratory patterns acquired during respiratory gating treatment in more than 300 patients. A total 331 patients treated with respiratory-gated carbon-ion beam therapy were selected from a group of patients with thoracic and abdominal conditions. Respiratory data were acquired for a total of 3,171 fractions using an external respiratory sensing monitor and evaluated for respiratory cycle, duty cycle, magnitude of baseline drift, and intrafractional/interfractional peak inhalation/exhalation positional variation. Results for the treated anatomical sites and patient positioning were compared. Mean ± SD respiratory cycle averaged over all patients was 4.1 ± 1.3 s. Mean ± SD duty cycle averaged over all patients was 36.5 ± 7.3 %. Two types of baseline drift were seen, the first decremental and the second incremental. For respiratory peak variation, the mean intrafractional variation in peak-inhalation position relative to the amplitude in the first respiratory cycle (15.5 ± 9.3 %) was significantly larger than that in exhalation (7.5 ± 4.6 %). Interfractional variations in inhalation (17.2 ± 18.5 %) were also significantly greater than those in exhalation (9.4 ± 10.0 %). Statistically significant differences were observed between patients in the supine position and those in the prone position in mean respiratory cycle, duty cycle, and intra-/interfractional variations. We quantified the characteristics of the respiratory curve based on a large number of respiratory data obtained during treatment. These results might be useful in improving the accuracy of respiratory-gated treatment