Effective string description of confining flux tubes

We review the current knowledge about the theoretical foundations of the effective string theory for confining flux tubes and the comparison of the predictions to pure gauge lattice data. A concise presentation of the effective string theory is provided, incorporating recent developments. We summarize the predictions for the spectrum and the profile/width of the flux tube and their comparison to lattice data. The review closes with a short summary of open questions for future research.Comment: 21 pages, 8 figures, Contribution to IJMPA special issue "Lattice gauge theory beyond QCD

Probing boundary-corrections to Nambu-Goto open string energy levels in 3d SU(2) gauge theory

We measure the energy levels of the excitations of the flux tube between static quark and antiquark in three-dimensional SU(2) gauge theory. Combining exponential error reduction techniques and a variational method we are able to reduce the errors for the excited states significantly and to extract excited states in distinct parity and charge conjugation channels. It is conjectured that the infrared behavior (at large q\bar{q} separation R) of the flux tube is governed by an effective string theory. Indeed previous simulations show good agreement between lattice data and predictions from Nambu-Goto string theory. Recently, new results on the effective string theory obtained corrections to the Nambu-Goto predictions and showed that for the open string in three dimensions first corrections should appears at order 1/R^4. They correspond to boundary terms in the worldsheet field theory. These corrections are presumably small for the ground state, but significantly larger for the excited states and lift the degeneracies of the free theory. Assuming this functional form of the correction, we obtain for the coefficient b_2=-0.5(2)(2).Comment: 20 pages, 7 figures; v2: Style changed to JHEP. Typos corrected and minor changes in the conclusions and the final results. Revised version to match published versio

Thermal Correlators in the \rho\ channel of two-flavor QCD

We present a lattice QCD calculation with two dynamical flavors of the isovector vector correlator in the high-temperature phase. We analyze the correlator in terms of the associated spectral function, for which we review the theoretical expectations. In our main analysis, we perform a fit for the difference of the thermal and vacuum spectral functions, and we use an exact sum rule that constrains this difference. We also perform a direct fit for the thermal spectral function, and obtain good agreement between the two analyses for frequencies below the two-pion threshold. Under the assumption that the spectral function is smooth in that region, we give an estimate of the electrical conductivity.Comment: (1+25) pages, 11 figure

Charge transport and vector meson dissociation across the thermal phase transition in lattice QCD with two light quark flavors

We compute and analyze correlation functions in the isovector vector channel at vanishing spatial momentum across the deconfinement phase transition in lattice QCD. The simulations are carried out at temperatures $T/T_c=0.156, 0.8, 1.0, 1.25$ and $1.67$ with $T_c\simeq203$MeV for two flavors of Wilson-Clover fermions with a zero-temperature pion mass of $\simeq270$MeV. Exploiting exact sum rules and applying a phenomenologically motivated ansatz allows us to determine the spectral function $\rho(\omega,T)$ via a fit to the lattice correlation function data. From these results we estimate the electrical conductivity across the deconfinement phase transition via a Kubo formula and find evidence for the dissociation of the $\rho$ meson by resolving its spectral weight at the available temperatures. We also apply the Backus-Gilbert method as a model-independent approach to this problem. At any given frequency, it yields a local weighted average of the true spectral function. We use this method to compare kinetic theory predictions and previously published phenomenological spectral functions to our lattice study.Comment: 28 pages, 6 figure

Tinjauan Yuridis Hubungan Fungsional Antara Penyidik Dan Penuntut Umum Dalam Proses Pemeriksaan Perkara Pidana

Kitab Undang-Undang Hukum Acara Pidana mengatur antara lain tugas dan wewenang masing-masing penegak hukum didalam pemeriksaan perkara tindak pidana. Tugas penyidikan dilakukan oleh pihak Kepolisian sedangkan tugas penuntutan terhadap pelaku tindak pidana dilakukan oleh pihak Kejaksaan. Walaupun tugas kepolisian dan kejaksaan berbeda dan terpisah satu denga yang lainnya, tetapi diantara mereka tetap ada hubungan yang bersifat fungsional. Hal ini diseabkan pemeriksaan tindak pidana itu berproses yang dimulai dari penyidikan, penuntutan dan berakhir degan pemeriksaan di pengadilan. Penyidik dilakukan oleh kepolisian demi untuk kepentigan penuntutan atau dengan kata lain penuntutan tidak bisa dilakukan kalau tidak ada hasil penyidikan yang dilakukan oleh kepolisian. Hubungan fungsional antara penyidik dengan penuntut umum dapat diketahui dengan adanya ketentuan yang diatur dalam pasal 109 dan 110 KUHAP. Pasal 109 KUHAP mengatur tentang penyidik yang telah memulai penyidikannya memberitahukan hal tersebut kpada penuntut umum. Kalaupun penyidik menghentikan penyidikaanya maka hal itu juga diberitahukan kepada penuntut umum. Pasal 110 KUHAP mengatur yaitu dalam hal penyidikan telah selesai melakukan penyidikan, penyidik wajib segera menyerahkan berkas perkara kepada penuntut umum. Dalam hal penutut umum berpendapat bahwa hasil penyidikan belum lenkap, maka penuntut umum segerah mengembalikan berkas tersebut kepada penyidik disertai petunjuk untuk di lengka

An estimate for the thermal photon rate from lattice QCD

We estimate the production rate of photons by the quark-gluon plasma in lattice QCD. We propose a new correlation function which provides better control over the systematic uncertainty in estimating the photon production rate at photon momenta in the range {\pi}T/2 to 2{\pi}T. The relevant Euclidean vector current correlation functions are computed with $N_{\mathrm f}$ = 2 Wilson clover fermions in the chirally-symmetric phase. In order to estimate the photon rate, an ill-posed problem for the vector-channel spectral function must be regularized. We use both a direct model for the spectral function and a model-independent estimate from the Backus-Gilbert method to give an estimate for the photon rate.Comment: 15 pages, 11 figures, talk presented at 35th annual International Symposium on Lattice Field Theory, 18-24 June 2017, Granada, Spai

Antiscreening of the Ampere force in QED and QCD plasmas

The static forces between electric charges and currents are modified at the loop level by the presence of a plasma. While electric charges are screened, currents are not. The effective coupling constant at long distances is enhanced in both cases as compared to the vacuum, and by different amounts, a clear sign that Lorentz symmetry is broken. We investigate these effects quantitatively, first in a QED plasma and secondly using non-perturbative simulations of QCD with two light degenerate flavors of quarks.Comment: 17 pages, 8 figure