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High Energy Physics - Lattice (hep-lat) updates on the e-print archive

Published: 2018-02-22T20:30:00-05:00


Mass spectrum of $2$-dimensional $\mathcal{N}=(2,2)$ super Yang-Mills theory on the lattice. (arXiv:1802.07797v1 [hep-lat])

In the present work we analyse $\mathcal{N}=(2,2)$ supersymmetric Yang-Mills (SYM) theory in two dimensions by means of lattice simulations. The theory arises as dimensional reduction of $\mathcal{N}=1$ SYM theory in four dimensions. As in other gauge theories with extended supersymmetry, the classical scalar potential has flat directions which may destabilize numerical simulations. In addition, the fermion determinant need not be positive and this sign-problem may cause further problems in a stochastic treatment. We demonstrate that $\mathcal{N}=(2,2)$ super Yang-Mills theory has actually no sign problem and that the flat directions are lifted and thus stabilized by quantum corrections. Only the bare mass of the scalars experience a finite additive renormalization in this finite theory. On various lattices with different lattice constants we determine the scalar masses and hopping parameters for which the supersymmetry violating terms are minimal. By studying four Ward identities and by monitoring the $\pi$-mass we show that supersymmetry is indeed restored in the continuum limit. In the second part we calculate the masses of the low-lying bound states. We find that in the infinite-volume and supersymmetric continuum limit the Veneziano-Yankielowicz super-multiplet becomes massless and the Farrar-Gabadadze-Schwetz super-multiplet decouples from the theory. In addition, we estimate the masses of the excited mesons in the Veneziano-Yankielowicz multiplet. We observe that the gluino-glueballs have comparable masses to the excited mesons.

Gradient flow and the Wilsonian renormalization group flow. (arXiv:1802.07897v1 [hep-th])

The gradient flow is evolution of fields and physical quantities along a dimensionful parameter~$t$, the flow time. We give a simple argument that relates this gradient flow and the Wilsonian renormalization group (RG) flow. We then illustrate the Wilsonian RG flow on the basis of the gradient flow in two examples which possess an infrared fixed point, the 4D many-flavor gauge theory and the 3D $O(N)$ linear sigma model.

Comment on "Are two nucleons bound in lattice QCD for heavy quark masses? - Sanity check with L\"uscher's finite volume formula -". (arXiv:1705.09239v3 [hep-lat] UPDATED)

In this comment, we address a number of erroneous discussions and conclusions presented in a recent preprint by the HALQCD collaboration, arXiv:1703.07210. In particular, we demonstrate that lattice QCD determinations of bound states at quark masses corresponding to a pion mass of $m_\pi = 806$ MeV are robust, and that the phases shifts extracted by the NPLQCD collaboration for these systems pass all of the 'sanity checks' introduced in arXiv:1703.07210.

The new $a_1(1420)$ state: structure, mass and width. (arXiv:1711.05977v2 [hep-ph] UPDATED)

The structure, spectroscopic parameters and width of the resonance with quantum numbers $J^{PC}=1^{++}$ discovered by the COMPASS Collaboration and classified as the $a_1(1420)$ meson are examined in the context of QCD sum rule method. In the calculations the axial-vector meson $a_1(1420)$ is treated as a four-quark state with the diquark-antidiquark structure. The mass and current coupling of $a_1(1420)$ are evaluated using QCD two-point sum rule approach. Its observed decay mode $a_1(1420) \to f_0(980)\pi$, and kinematically allowed ones, namely $a_1 \to K^{\ast \pm}K^{\mp}$, $a_1 \to K^{\ast 0} \bar{K}^{0}$ and $a_1 \to \bar {K}^{\ast 0} K^{0}$ channels are studied employing QCD sum rules on the light-cone. Our prediction for the mass of the $a_1(1420)$ state $m_{a_{1}}=1416_{-79}^{+81}\ \mathrm{MeV}$ is in excellent agreement with the experimental result. Width of this state $ \Gamma=145.52 \pm 20.79 \mathrm{MeV}$ within theoretical and experimental errors is also in accord with the COMPASS data.