952 research outputs found
Supersymmetric Boost on Intersecting D-branes
We study the effect of the Born-Infeld electric field on the supersymmetric
configuration of various composite D-branes. We show that the generic values of
the electric field do not affect the supersymmetry but, as it approaches
keeping the magnetic field finite, various combinations of the
magnetic fields allow up to 8 supersymmetries. We also explore the unbroken
supersymmetries for two intersecting D-strings which are in uniform or relative
motion. For a finite uniform Lorentz boost, 16 supersymmetries are guaranteed
only when they are parallel. For an infinite one, 8 supersymmetries are
preserved only when both the D-strings are oriented to the forward or backward
direction of the boost. Under a finite relative boost, 8 supersymmetries are
preserved only when the intersecting angle is less than and the
intersecting point moves at the speed of light. As for an infinite relative
boost, 8 supersymmetries are preserved regardless of the values of the
intersecting angle.Comment: 27 pages using REVTeX4, 7 figure
Open/Closed String Dualities and Seiberg Duality from Geometric Transitions in M-theory
We propose a general method to study open/closed string dualities from
transitions in M theory which is valid for a large class of geometrical
configurations. By T-duality we can transform geometrically engineered
configurations into N = 1 brane configurations and study the transitions of the
corresponding branes by lifting the configurations to M-theory. We describe the
transformed degenerated M5 branes and extract the field theory information on
gluino condensation by factorization of the Seiberg-Witten curve. We also
include massive flavors and orientifolds and discuss Seiberg duality which
appears in this case as a birational flop. After the transition, the Seiberg
duality becomes an abelian electric-magnetic duality.Comment: 30 pages, 3 figures, Late
Îł-Cyclodextrin Metal-Organic Frameworks: Do Solvents Make a Difference?
Conventionally, methanol is the solvent of choice in the synthesis of gamma-cyclodextrin metal-organic frameworks (Îł-CD-MOFs), but using ethanol as a replacement could allow for a more food-grade synthesis condition. Therefore, the aim of the study was to compare the Îł-CD-MOFs synthesised with both methanol and ethanol. The Îł-CD-MOFs were characterised by scanning electron microscopy (SEM), surface area and pore measurement, Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (PXRD). The encapsulation efficiency (EE) and loading capacity (LC) of the Îł-CD-MOFs were also determined for curcumin, using methanol, ethanol and a mixture of the two as encapsulation solvent. It was found that Îł-CD-MOFs synthesised by methanol and ethanol do not differ greatly, the most significant difference being the larger crystal size of Îł-CD-MOFs crystallised from ethanol. However, the change in solvent significantly influenced the EE and LC of the crystals. The higher solubility of curcumin in ethanol reduced interactions with the Îł-CD-MOFs and resulted in lowered EE and LC. This suggests that different solvents should be used to deliberately manipulate the EE and LC of target compounds for better use of Îł-CD-MOFs as their encapsulating and delivery agents
New study of the isotensor pi-pi interaction
With t-channel rho, f2(1270) exchange and the pi pi -> rho rho -> pi pi box
diagram contribution, we reproduce the pi pi isotensor S-wave and D-wave
scattering phase shifts and inelasticities up to 2.2 GeV quite well in a
K-matrix formalism. The t-channel rho exchange provides repulsive negative
phase shifts while the t-channel f2(1270) gives an attractive force to increase
the phase shifts for pi pi scattering above 1 GeV, and the coupled-channel box
diagram causes the inelasticities. The implication to the isoscalar pi pi
S-wave interaction is discussed.Comment: 17 pages, 5 figure
RG flows from Spin(7), CY 4-fold and HK manifolds to AdS, Penrose limits and pp waves
We obtain explicit realizations of holographic renormalization group (RG)
flows from M-theory, from E^{2,1} \times Spin(7) at UV to AdS_4 \times
\tilde{S^7} (squashed S^7) at IR, from E^{2,1} \times CY4 at UV to AdS_4 \times
Q^{1,1,1} at IR, and from E^{2,1} \times HK (hyperKahler) at UV to AdS_4 \times
N^{0,1,0} at IR. The dual type IIA string theory configurations correspond to
D2-D6 brane systems where D6 branes wrap supersymmetric four-cycles. We also
study the Penrose limits and obtain the pp-wave backgrounds for the above
configurations. Besides, we study some examples of non-supersymmetric and
supersymmetric flows in five-dimensional gauge theories.Comment: 42 pages, 6 eps figures, typos and misprints correcte
Supersymmetry, G-flux and Spin(7) manifolds
In this note we study warped compactifications of M-theory on manifolds of
Spin(7) holonomy in the presence of background 4-form flux. The explicit form
of the superpotential can be given in terms of the self -dual Cayley
calibration on the Spin(7) manifold, in agreement with the general formula
propsed in hep-th/9911011
Penta-quark states with hidden charm and beauty
More and more hadron states are found to be difficult to be accommodated by
the quenched quark models which describe baryons as 3-quark states and mesons
as antiquark-quark states. Dragging out an antiquark-quark pair from the gluon
field in hadrons should be an important excitation mechanism for hadron
spectroscopy. Our recent progress on the penta-quark states with hidden charm
and beauty is reviewed.Comment: Plenary talk at the 5th Asia-Pacific Conference on Few-Body Problems
in Physics 2011 (APFB2011), 22-26 Aug., 2011, Seoul, Kore
Brane Tilings and M2 Branes
Brane tilings are efficient mnemonics for Lagrangians of N=2
Chern-Simons-matter theories. Such theories are conjectured to arise on
M2-branes probing singular toric Calabi-Yau fourfolds. In this paper, a simple
modification of the Kasteleyn technique is described which is conjectured to
compute the three dimensional toric diagram of the non-compact moduli space of
a single probe. The Hilbert Series is used to compute the spectrum of
non-trivial scaling dimensions for a selected set of examples.Comment: 47 pages, 23 figure
Quiver theories, soliton spectra and Picard-Lefschetz transformations
Quiver theories arising on D3-branes at orbifold and del Pezzo singularities
are studied using mirror symmetry. We show that the quivers for the orbifold
theories are given by the soliton spectrum of massive 2d N=2 theory with
weighted projective spaces as target. For the theories obtained from the del
Pezzo singularities we show that the geometry of the mirror manifold gives
quiver theories related to each other by Picard-Lefschetz transformations, a
subset of which are simple Seiberg duals. We also address how one indeed
derives Seiberg duality on the matter content from such geometrical transitions
and how one could go beyond and obtain certain ``fractional Seiberg duals.''
Moreover, from the mirror geometry for the del Pezzos arise certain Diophantine
equations which classify all quivers related by Picard-Lefschetz. Some of these
Diophantine equations can also be obtained from the classification results of
Cecotti-Vafa for the 2d N=2 theories.Comment: 34 pages, 11 figure
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