119095268
Cosmological Constant as Vacuum Energy Density of Quantum Field Theories on Noncommutative Spacetime
We propose a new approach to understand hierarchy problem for cosmological constant in terms of considering noncommutative nature of space-time. We calculate that vacuum energy density of the noncommutative quantum field theories in nontrivial background, which admits a smaller cosmological constant by introducing an higher noncommutative scale $\mu_{NC}\sim M_p$. The result $\rho_\Lambda\sim 10^{-6}\Lambda_{SUSY}^8M_p^4/\mu_{NC}^8$ yields cosmological constant at the order of current observed value for supersymmetry breaking scale at 10TeV. It is the same as Banks' phenomenological formula for cosmological constant.
119481484
Open spin chain and open spinning string
In this Letter, we study the open spinning strings and their SYM duals. A new class of folded open spinning strings is found. At planar one-loop level in SYM, by solving the thermodynamic limit of the Bethe ansatz equations for an integrable open spin chain, we find good agreement with string theory predictions for energies of both circular and folded two-spin solutions. A universal relation between the open and closed spinning strings is verified in the spin chain approach.
8346546
Integrable open spin chain in super Yang-Mills and the plane-wave/SYM duality
We investigate the integrable structures in an = 2 superconformal Sp(N) Yang-Mills theory with matter, which is dual to an open+closed string system. We restrict ourselves to the BMN operators that correspond to free string states. In the closed string sector, an integrable structure is inherited from its parent theory, = 4 SYM. For the open string sector, the planar one-loop mixing matrix for gauge invariant holomorphic scalar operators is identified with the hamiltonian of an integrable SU(3) open spin chain. Using the K-matrix formalism we identify the integrable open-chain boundary conditions that correspond to string boundary conditions. The solutions to the algebraic Bethe ansatz equations (ABAE) with a few impurities are shown to recover the anomalous dimensions that exactly match the spectrum of free open string in the plane-wave background. We also discuss the properties of the solutions of ABAE beyond the BMN regime.
118980773
Green Functions of N=1 SYM and Radial/Energy-Scale Relation
We study counter-terms of one- and two-point Green functions of some special operators in ${\cal N}=1$ SYM from their SUGRA duals from the consideration of AdS/CFT or gauge/gravity correspondence. We consider both the Maldacena-Nunez solution and the Klebanov-Strassler-Tseytlin solution that are proposed to be SUGRA duals of ${\cal N}=1$ SYM. We obtain radial/energy-scale relation for each solution by comparing SUGRA calculations with the field theory results. Using these relations we evaluate the $\beta$-function of ${\cal N}=1$ SYM. We find that the leading order term can be accurately obtained for both solutions and the higher order terms exhibit some ambiguities. We discuss the origin of these ambiguities and conclude that more studies are needed to check whether these SUGRA solutions are exactly dual to ${\cal N}=1$ SYM.
119479056
Integrable spin chain and operator mixing in N=1,2 supersymmetric theories
Abstract We study operator mixing, due to planar one-loop corrections, for composite operators in D =4 supersymmetric theories. We present some N =1,2 Yang–Mills and Wess–Zumino models, in which the planar one-loop anomalous dimension matrix in the sector of holomorphic scalars is identified with the Hamiltonian of an integrable quantum spin chain with SU (3) or SU (2) symmetry, even if the theory is away from the conformal points. This points to a more universal origin of the integrable structure beyond superconformal symmetry. We also emphasize the role of the superpotential in the appearance of the integrable structure. The computations of operator mixing in our examples by solving Bethe ansatz equations show some new features absent in N =4 SYM.
16712339
Intersecting branes and adding flavors to the Maldacena-Nunez background
Following a proposal in ref. [3], we study adding flavors into the Maldacena-Nunez background. It is achieved by introducing spacetime filling D9-branes or intersecting D5'-branes into the background with a wrapping D5-brane. Both D9-branes and D5'-branes can be spacetime filling from the 5D bulk point of view. At the probe limit it corresponds to introducing non-chiral fundamental flavors into the dual = 1 SYM. We propose a method to twist the fundamental flavor which has to involve open string charge. It reflects the fact that coupling fundamental matter to SYM in the dual string theory corresponds to adding an open string sector.
118578666
Initial conditions for the modified evolution of fragmentation functions in the nuclear medium
Initial conditions are required to solve medium modified DGLAP (mDGLAP) evolution equations for modified fragmentation functions due to multiple scatterings and parton energy loss. Such initial conditions should in principle include energy loss for partons at scale $Q_0$ above which mDGLAP evolution equations can be applied. Several models for the initial condition motivated by induced gluon bremsstrahlung in perturbative QCD are used to calculate the modified fragmentation functions in nuclear medium and to extract the jet transport parameter $\hat q$ from fits to experimental data in deeply inelastic scattering (DIS) off nuclei. The model with a Poisson convolution of multiple gluon emissions is found to provide the overall best $\chi^2$/d.o.f. fit to the HERMES data and gives a value of $\hat q_0 \approx 0.020 \pm 0.005$ GeV$^2$/fm at the center of a large nucleus.
118559274
Spin-Orbit Interaction of Nuclear Shell Structure
Single particle spin-orbit interaction energy problem in nuclear shell structure is solved through negative harmonic oscillator in the self-similar-structure shell model (SSM) [4] and considering quarks' contributions on single particle spin and orbit momentum. The paper demonstrates that single particle motion in normal nuclei is described better by SSM negative harmonic oscillator than conventional shell model positive harmonic oscillator[1][2][3]. The proposed theoretical formula for spin orbit interaction energy agrees well to experiment measurements.
119280465
Characterizing Temporal Structure of the Relativistic Electron Bunch
Using proper beam energy chirp and the undulator detuning effect, we propose a modified optical replica synthesizer scheme to characterize the temporal structure of a relativistic electron bunch, which predicts a 100-fs temporal resolution in numerical simulation. The proof of principle experiment demonstrates a peak current of 9 A and a slice energy spread of about 0.5 keV for the uncompressed electron beam of the Shanghai Deep UV Free Electron Laser Facility.
17657545
Multiple parton scattering in nuclei: gauge invariance
Within the framework of a generalized collinear factorization for multiple parton scattering in nuclear medium, twist-4 contributions to DIS off a large nucleus can be factorized as a convolution of hard parts and two-parton correlation functions. The hard parts for the quark scattering in the light-cone gauge correspond to interaction with a transverse (physical) gluon in the target, while they are given by the second derivative of the cross section with a longitudinal gluon in the covariant gauge. We provide a general proof of the equivalence of the hard parts in the light-cone and covariant gauge. We further demonstrate the equivalence in calculations of twist-4 contributions to semi-inclusive cross section of DIS in both lowest order and next leading order. Calculations of the nuclear transverse momentum broadening of the struck quark in the light-cone and covariant gauge are also discussed.
123054554
The precision measurement of the neutron spin structure function using polarized helium-3 target
Using a 48.6 GeV polarized electron beam scattering off a polarized {sup 3}He target at Stanford Linear Accelerator Centre (SLAC), they measured the neutron spin structure function g{sub 1}{sup n} over kinematic(x) ranging 0.014 < x <0.7 and 1 < Q{sup 2} < 17GeV{sup 2}. The measurement gave the integral result over the neutron spin structure function {integral}{sub 0.014}{sup 0.7} g{sub 1}{sup n}(x)dx = -0.036 {+-} 0.004(stat) {+-} 0.005(syst) at an average Q{sup 2} = 5GeV{sup 2}. Along with the proton results from SLAC E143 experiment (0.03 < x) and SMC experiment (0.014 < x < 0.03), they find the Bjorken sum rule appears to be largely saturated by the data integrated down to x of 0.014. However, they observe relatively large values for g{sub 1}{sup n} at low x. The result calls into question the usual methods (Regge theory) for extrapolating to x = 0 to find the full neutron integral {integral}{sub 0}{sup t} g{sub 1}{sup n}(x) dx, needed for testing the Quark-Parton Model (QMP).