28 research outputs found
Bound States of Dimensionally Reduced {SYM}_{2+1} at Finite N
We consider the dimensional reduction of N=1 {SYM}_{2+1} to 1+1 dimensions.
The gauge groups we consider are U(N) and SU(N), where N is finite. We
formulate the continuum bound state problem in the light-cone formalism, and
show that any normalizable SU(N) bound state must be a superposition of an
infinite number of Fock states. We also discuss how massless states arise in
the DLCQ formulation for certain discretizations.Comment: 14 pages, REVTE
Can DLCQ test the Maldacena Conjecture?
We consider the Maldacena conjecture applied to the near horizon geometry of
a D1-brane in the supergravity approximation and consider the possibility of
testing the conjecture against the boundary field theory calculation using
DLCQ. We propose the two point function of the stress energy tensor as a
convenient quantity that may be computed on both sides of the correspondence.
On the supergravity side, we may invoke the methods of Gubser, Klebanov,
Polyakov, and Witten. On the field theory side, we derive an explicit
expression for the two point function in terms of data that may be extracted
from a DLCQ calculation at a given harmonic resolution. This gives rise to a
well defined numerical algorithm for computing the two point function, which we
test in the context of free fermions and the 't Hooft model. For the
supersymmetric Yang-Mills theory with 16 supercharges that arises in the
Maldacena conjecture, the algorithm is perfectly well defined, although the
size of the numerical computation grows too fast to admit any detailed analysis
at present, and our results are only preliminary. We are, however, able to
present more detailed results on the supersymmetric DLCQ computation of the
stress energy tensor correlators for two dimensional Yang Mills theories with
(1,1) and (2,2) supersymmetries.Comment: 19 pages, 5 figure
Matrix Theories from Reduced SU(N) Yang-Mills with Adjoint Fermions
We consider a dimensional reduction of 3+1 dimensional SU(N) Yang-Mills
theory coupled to adjoint fermions to obtain a class of 1+1 dimensional matrix
field theories. We derive the quantized light-cone Hamiltonian in the
light-cone gauge A_- = 0 and large-N limit, and then solve for the masses,
wavefunctions and structure functions of the color singlet ``meson-like'' and
``baryon-like'' boundstates. Among the states we study are many massless
string-like states that can be solved for exactly.Comment: 13 pages, Revtex, one PS figur
Fabrication of deformable patient-specific AAA models by material casting techniques
BackgroundAbdominal Aortic Aneurysm (AAA) is a balloon-like dilatation that can be life-threatening if not treated. Fabricating patient-specific AAA models can be beneficial for in-vitro investigations of hemodynamics, as well as for pre-surgical planning and training, testing the effectiveness of different interventions, or developing new surgical procedures. The current direct additive manufacturing techniques cannot simultaneously ensure the flexibility and transparency of models required by some applications. Therefore, casting techniques are presented to overcome these limitations and make the manufactured models suitable for in-vitro hemodynamic investigations, such as particle image velocimetry (PIV) measurements or medical imaging.MethodsTwo complex patient-specific AAA geometries were considered, and the related 3D models were fabricated through material casting. In particular, two casting approaches, i.e. lost molds and lost core casting, were investigated and tested to manufacture the deformable AAA models. The manufactured models were acquired by magnetic resonance, computed tomography (CT), ultrasound imaging, and PIV. In particular, CT scans were segmented to generate a volumetric reconstruction for each manufactured model that was compared to a reference model to assess the accuracy of the manufacturing process.ResultsBoth lost molds and lost core casting techniques were successful in the manufacturing of the models. The lost molds casting allowed a high-level surface finish in the final 3D model. In this first case, the average signed distance between the manufactured model and the reference was (â0.2±0.2) mm. However, this approach was more expensive and time-consuming. On the other hand, the lost core casting was more affordable and allowed the reuse of the external molds to fabricate multiple copies of the same AAA model. In this second case, the average signed distance between the manufactured model and the reference was (0.1±0.6) mm. However, the final modelâs surface finish quality was poorer compared to the model obtained by lost molds casting as the sealing of the outer molds was not as firm as the other casting technique.ConclusionsBoth lost molds and lost core casting techniques can be used for manufacturing patient-specific deformable AAA models suitable for hemodynamic investigations, including medical imaging and PIV
Quality of images with toric intraocular lenses
Purpose: To objectively evaluate the image quality obtained with toric intraocular lenses (IOLs) when misaligned from the intended axis. Setting: University Eye Clinic and the Department of Industrial and Information Engineering, University of Trieste, Trieste, Italy. Design: Experimental study. Methods: An experimental optoelectronic test bench was created. It consisted of a high-resolution monitor to project target images and an artificial eye. The system simulates the optical and geometric characteristics of the human eye with an implanted toric IOL. A 3.00 diopters corneal astigmatism was simulated. Images reproduced by the optical system were captured according to different IOL axis positions. The quality of each image was analyzed using the visual information fidelity (VIF) criterion. The VIF reduction was calculated at each IOL rotational step. Results: A 5-degree IOL axis rotation from the intended position determined a decay in the image quality of 7.03%. Ten degrees of IOL rotation caused an 11.09% decay of relative VIF value. For a 30-degree rotation, the VIF decay value was 45.85%. Finally, the image decay with no toric correction was 56.70%. Conclusions: The more the objective quality of the image decays progressively, the further the axis of the IOL is rotated from its intended position. The reduction in image quality obtained after 30 degrees of toric IOL rotation was less than 50% and after 45 degrees, the image quality was the same as that of no toric correction