119224646
Giant gravitons and correlators
A bstractWe calculate non-extremal correlators of Schur polynomials and single trace operators. We analyse their dual descriptions from the approach of the variation of DBI and WZ actions of the giant gravitons. We show a regularization procedure under which the extremal correlators of Schur polynomials and single trace operators match exactly with string theory computation. Other aspects of the extremal and non-extremal correlators are also discussed.
118578636
Nonplanar integrability
In this article we study operators with a dimension Δ ∼ O(N) and show that simple analytic expressions for the action of the dilatation operator can be found. The operators we consider are restricted Schur polynomials. There are two distinct classes of operators that we consider: operators labeled by Young diagrams with two long columns or two long rows. The main complication in working with restricted Schur polynomials is in building a projector from a given Sn+m irreducible representation to an Sn × Sm irreducible representation (both specified by the labels of the restricted Schur polynomial). We give an explicit construction of these projectors by reducing it to the simple problem of addition of angular momentum in ordinary non-relativistic quantum mechanics. The diagonalization of the dilatation operator reduces to solving three term recursion relations. The fact that the recursion relations have only three terms is a direct consequence of the weak mixing at one loop of the restricted Schur polynomials. The recursion relations can be solved exactly in terms of symmetric Kravchuk polynomials or in terms of Clebsch-Gordan coefficients. This proves that the dilatation operator reduces to a decoupled set of harmonic oscillators and therefore it is integrable.
15191903
Bubbling AdS space and 1/2 BPS geometries
We consider all 1/2 BPS excitations of AdS × S configurations in both type-IIB string theory and M-theory. In the dual field theories these excitations are described by free fermions. Configurations which are dual to arbitrary droplets of free fermions in phase space correspond to smooth geometries with no horizons. In fact, the ten dimensional geometry contains a special two dimensional plane which can be identified with the phase space of the free fermion system. The topology of the resulting geometries depends only on the topology of the collection of droplets on this plane. These solutions also give a very explicit realization of the geometric transitions between branes and fluxes. We also describe all 1/2 BPS excitations of plane wave geometries. The problem of finding the explicit geometries is reduced to solving a Laplace (or Toda) equation with simple boundary conditions. We present a large class of explicit solutions. In addition, we are led to a rather general class of AdS5 compactifications of M-theory preserving = 2 superconformal symmetry. We also find smooth geometries that correspond to various vacua of the maximally supersymmetric mass-deformed M2 brane theory. Finally, we present a smooth 1/2 BPS solution of seven dimensional gauged supergravity corresponding to a condensate of one of the charged scalars.
118796950
Studies on 1/4 BPS and 1/8 BPS geometries
We analyze more explicitly four sectors of 1/4 BPS geometries and 1/8 BPS geometries, corresponding to BPS states in N=4 SYM, constructed previously. These include the states with several SO(6) angular momenta as well as those with SO(4) AdS spins. We also discuss their relations to the dual gauge theory.
118812509
BPS geometry, AdS/CFT, and string theory
We first study BPS geometries dual to half-BPS states of field theories with 32 supercharges. These field theories are N = 4 SYM on R×S3, M2 brane theory and M5 brane theory. The dynamics of the half-BPS states in N = 4 SYM is reduced to a matrix quantum mechanics, and they are characterized by droplets on the two dimensional phase space. The geometries dual to these states are specified by boundary conditions on a two-plane, which are identified as the phase space. The phase space gives unified description of half-BPS perturbative and non-perturbative excitations aboveAdS5×S. The half-BPS geometries in the M theory case are described by a Toda equation with similar but more complicated boundary conditions on a two-plane. We then study BPS geometries dual to the vacua of field theories with 16 supercharges. The first class of theory has a bosonic U(1) × SO(4) × SO(4) symmetry, they include the mass deformed M2 brane theory, D4 or M5 brane theory on S3, and intersecting NS5 brane theory. Their vacua are characterized by droplets on a cylinder or torus. The second class of theory has a SU(2|4) symmetry, they include the 0+1d plane-wave matrix model, 2+1d super Yang-Mills theory on R×S2, N = 4 Super Yang-Mills on R×S/Zk, and NS5 brane theory on R× S5. The vacua of these theories are described by electrostatic configurations with many disks under external potential. The region between disks describe NS5 brane geometries. Finally we study instanton solutions and superpotentials for the vacua of the plane-wave matrix model and 2+1d super Yang-Mills theory and discuss the emergence of the vacuum geometries.
119367735
Instantons, supersymmetric vacua, and emergent geometries
We study instanton solutions and superpotentials for the large number of vacua of the plane-wave matrix model and a 2+1 dimensional Super Yang-Mills theory on RxS{sup 2} with 16 supercharges. We get the superpotential in the weak-coupling limit from the gauge theory description. We study the gravity description of these instantons. Perturbatively, with respect to a background, they are Euclidean branes wrapping cycles in the dual gravity background. Moreover, the superpotential can be given by the energy of the electric charge system characterizing each vacuum. These charges are interpreted as the eigenvalues of matrices from a reduction for the 1/8 BPS sector of the gauge theories. We also discuss qualitatively the emergence of the extra spatial dimensions appeared on the gravity side.
118372786
GAMMA-RAY POLARIZATION OF THE SYNCHROTRON SELF-COMPTON PROCESS FROM A HIGHLY RELATIVISTIC JET
The high polarization observed in the prompt phase of some gamma-ray bursts invites extensive study of the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron self-Compton (SSC) process from a highly relativistic jet. Amagnetic-dominated, baryon-loaded jet ejected from the central engine travels with a large Lorentz factor. Shells with slightly different velocities collide with each other and produce shocks. The shocks accelerate electrons to a power-law distribution and, at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. Synchrotron photons suffer from the Compton scattering (CS) process and then are detected by an observer located slightly off-axis. We analytically derive the formulae of photon polarization in the SSC process in two magnetic configurations: a magnetic field in the shock plane and perpendicular to the shock plane. We show that photons induced by the SSC process can be highly polarized, with the maximum polarization Pi similar to 24% in the energy band [0.5, 5] MeV. The polarization depends on the viewing angles, peaking in the plane perpendicular to the magnetic field. In the energy band [0.05, 0.5] MeV, in which most gamma-ray polarimeters are active, the polarization is about twice that in the Thomson limit, reaching Pi similar to 20%. This implies that the Klein-Nishina effect, which is often neglected in the literature, should be carefully considered.
119108453
Effects of spacetime anisotropy on the galaxy rotation curves
The observations on galaxy rotation curves show significant discrepancies from the Newtonian theory. This issue could be explained by the effect of the anisotropy of the spacetime. Conversely, the spacetime anisotropy could also be constrained by the galaxy rotation curves. Finsler geometry is a kind of intrinsically anisotropic geometry. In this paper, we study the effect of the spacetime anisotropy at galactic scales in the Finsler spacetime. It is found that the Finslerian model has close relations with the Milgrom’s MOND. By performing the best-fit procedure to the galaxy rotation curves, we find that the anisotropic effects of the spacetime become significant when the Newtonian acceleration GM/r2 is smaller than the critical acceleration a0. Interestingly, the critical acceleration a0, although varies between different galaxies, is in the order of magnitude $cH_{0}/2\pi\sim10^{-10}~\mathrm{m\,s}^{-2}$.
122891013
New directions in lattice gauge theory
Abstract Three topics are presented which are among those being actively explored by the RBC collaboration. In the first we extend the regularization independent renormalization scheme of the Rome-Southampton group, applying it to matrix elements computed using the Fermilab heavy quark effective action. Next we discuss the use of G-parity boundary conditions to permit the direct calculation of physical, on-shell K → ππ amplitudes. Both a theoretical description of our approach and first numerical results from studying π − π states are given. Finally, a brief summary and present status of the QCDOC project is given.
118473600
Galaxy Rotation Curves in the Grumiller's Modified Gravity
The effective potential in the Grumiller's modified gravity includes the Newtonian potential and a Rindler term. The fitting to the rotation curve data of eight galaxies suggests a universal Rindler acceleration a approximate to 0.30 x 10(-10) ms(-2). We do a two-parameter fit first, with the mass-to-light ratio ((sic)(*)) and the Rindler acceleration (a) as free parameters. It is found that the data of six out of the eight galaxies fit well with the prediction of theory in the range 0 r less than or similar to 40 kpc, although the theoretical curves show a tendency of arising beyond this range. The Rindler accelerations of the six well-fitted galaxies have the same magnitude, with an average value (a) over bar approximate to 0.30 x 10(-10) ms(-2). Inspired by this fact, we then carry out a one-parameter ((sic)(*)) fit to the six galaxies, with a fixed at (a) over bar, and find that the theory can still reproduce the observation. The value of Rindler acceleration we get here is a quarter of that of Milgrom's modified Newtonian dynamics. For the rest two galaxies, NGC 5055 and DDO 154, the fitting results are significantly improved if the photometric scale length (h) is included as another free parameter.
117989993
Magnetically induced spin reorientation on the surface of a topological insulator (a surface magnetic topological insulator MBE film)
The surface of topological insulators is proposed as a promising platform for spintronics and quantum information applications. In particular, when time- reversal symmetry is broken, topological surface states are expected to exhibit a wide range of exotic spin phenomena for potential implementation in electronics. Such devices need to be fabricated using nanoscale artificial thin films. It is of critical importance to study the spin behavior of artificial topological MBE thin films associated with magnetic dopants, and with regards to quantum size effects related to surface-to-surface tunneling as well as experimentally isolate time-reversal breaking from non-intrinsic surface electronic gaps. Here we present observation of the first (and thorough) study of magnetically induced spin reorientation phenomena on the surface of a topological insulator. Our results reveal dramatic rearrangements of the spin configuration upon magnetic doping contrasted with chemically similar nonmagnetic doping as well as with quantum tunneling phenomena in ultra-thin high quality MBE films. While we observe that the spin rearrangement induced by quantum tunneling occurs in a time-reversal invariant fashion, we present critical and systematic observation of an out-of-plane spin texture evolution correlated with magnetic interactions, which breaks time-reversal symmetry, demonstrating microscopic TRB at a Kramers' point on the surface.