Conformal symmetry and light flavor baryon spectra

The degeneracy among parity pairs systematically observed in the N and Delta spectra is interpreted to hint on a possible conformal symmetry realization in the light flavor baryon sector in line with AdS_5/CFT_4. The case is made by showing that all the observed N and Delta resonances with masses below 2500 MeV distribute fairly well each over the first levels of a unitary representation of the conformal group, a representation that covers the spectrum of a quark-diquark system, placed directly on the AdS_5 cone, conformally compactified to R^1*S^3. The free geodesic motion on the S^3 manifold is described by means of the scalar conformal equation there, which is of the Klein-Gordon type. The equation is then gauged by the "curved" Coulomb potential that has the form of a cotangent function. Conformal symmetry is not exact, this because the gauge potential slightly modifies the conformal centrifugal barrier of the free geodesic motion. Thanks to this, the degeneracy between P11-S11 pairs from same level is relaxed, while the remaining states belonging to same level remain practically degenerate. The model describes the correct mass ordering in the P11-S11 pairs through the nucleon spectrum as a combined effect of the above conformal symmetry breaking, on the one side, and a parity change of the diquark from a scalar at low masses, to a pseudoscalar at higher masses, on the other. The quality of the wave functions is illustrated by calculations of realistic mean-square charge radii and electric charge form-factors on the examples of the proton, and the protonic P11(1440), and S11(1535) resonances. The scheme also allows for a prediction of the dressing function of an effective instantaneous gluon propagator from the Fourier transform of the gauge potential. We find a dressing function that is finite in the infrared and tends to zero at infinity.Comment: Latex, 5 figures, 2 tables; Paper upgraded in accord with the published version. Discussion on the meson sector include

Update on pion weak decay constants in nuclear matter

The QCD sum rule calculation of the in-medium pion decay constants using pseudoscalar-axial vector correlation function, $i \int d^4x e^{ip\cdot x} < \rho| T[{\bar d}(x) i \gamma_5 u (x) {\bar u}(0) \gamma_\mu \gamma_5 d (0)] | \rho>$ is revisited. In particular, we argue that the dimension 5 condensate, $_N + {1\over 8} < {\bar q} g_s \sigma \cdot {\cal G} q >_N$, which is crucial for splitting the time ($f_t$) and space ($f_s$) components of the decay constant, is not necessarily restricted to be positive. Its positive value is found to yield a tachyonic pion mass. Using the in-medium pion mass as an input, we fix the dimension 5 condensate to be around $-0.025 {\rm GeV}^2 \sim -0.019$ GeV$^2$. The role of the $N$ and $\Delta$ intermediate states in the correlation function is also investigated. The $N$ intermediate state is found not to contribute to the sum rules. For the $\Delta$ intermediate state, we either treat it as a part of the continuum or propose a way to subtract explicitly from the sum rules. With (and without) explicit $\Delta$ subtraction while allowing the in-medium pion mass to vary within 139 MeV $\le m_\pi^* \le$ 159 MeV, we obtain $f_s/f_\pi = 0.37 \sim 0.78$ and $f_t / f_\pi = 0.63 \sim 0.79$.Comment: 18 pages including 5 postscript figure

Anwendung von Lean-Prinzipien im Erdbau - Entwicklung eines Baustellenleitstands auf Basis von Virtual Reality

Die vorliegende Arbeit befasst sich mit der Entwicklung eines Baustellenleitstands auf Basis von Virtual Reality für den Erdbau unter Berücksichtigung des Lean Management. Hierbei konnte neben der erhöhten Verfügbarkeit von Informationen und deren transparenter Darstellung durch die Anwendung eines digitalen Kanban-Systems eine Steigerung der Produktionsleistung auf der Erdbaustelle nachgewiesen werden

Anwendung von Lean-Prinzipien im Erdbau - Entwicklung eines Baustellenleitstands auf Basis von Virtual Reality

Die vorliegende Arbeit befasst sich mit der Entwicklung eines Baustellenleitstands auf Basis von Virtual Reality für den Erdbau unter Berücksichtigung des Lean Management. Hierbei konnte neben der erhöhten Verfügbarkeit von Informationen und deren transparenter Darstellung durch die Anwendung eines digitalen Kanban-Systems eine Steigerung der Produktionsleistung auf der Erdbaustelle nachgewiesen werden

Earth­works Con­trol Automa­tion

Earthwork processes are influenced by a wide range of factors, including varying soil and weather conditions, machine related factors, traffic conditions, local site constraints and other human related factors. Dumpers and bulldozers are heavy duty equipment and there is need to optimise their operational efficiencies. Given dynamic nature of site and changing weather conditions, like temperature, precipitation or wind, can lead to process disturbance like complete restrictions on the site roads or a considerable slow down. Therefore, it is necessary to capture accurate data from site operations to reduce waste in earthwork processes. Even though various commercial vendors (e.g. Leica, Trimble) have started to provide commercial solutions to allow telematics operations (e.g. remote support, fleet management, grade control), costs of these solutions are prohibitive. Presented research proposes the use of low cost data capturing techniques and off-the-shelf technology components to collect real time and reliable data on Earthworks processes. This research aims to enhance earthworks efficiency through better utilisation of building vehicles and an improved information flow. On-site observations and anecdotal evidence suggest that waiting time for excavators and dumpers on Highways Agency’s schemes is a common occurrence. However, despite this evidence, there is a lack of real-time or archival data available on site operations and not enough effort is spent on gathering reliable and accurate data. In order to enable an optimised process, the need for an automated real-time data collection on construction sites is apparent

In-medium pion weak decay constants

In nuclear matter, the pion weak decay constant is separated into the two components $f_t, f_s$ corresponding to the time and space components of the axial-vector current. Using QCD sum rules, we compute the two decay constants from the pseudoscalar-axial vector correlation function in the matter $i \int d^4x~ e^{ip\cdot x} < \rho| T[{\bar d}(x) i \gamma_5 u (x)~ {\bar u}(0) \gamma_\mu \gamma_5 d (0)] | \rho>$. It is found that the sum rule for $f_t$ satisfies the in-medium Gell-Mann--Oakes--Renner (GOR) relation precisely while the $f_s$ sum rule does not. The $f_s$ sum rule contains the non-negligible contribution from the dimension 5 condensate $_N + {1\over 8} _N$ in addition to the in-medium quark condensate. Using standard set of QCD parameters and ignoring the in-medium change of the pion mass, we obtain $f_t =105$ MeV at the nuclear saturation density. The prediction for $f_s$ depends on values of the dimension 5 condensate and on the Borel mass. However, the OPE constrains that $f_s/f_t \ge 1$, which does not agree with the prediction from the in-medium chiral perturbation theory. Depending on the value of the dimension 5 condensate, $f_s$ at the saturation density is found to be in the range $112 \sim 134$ MeV at the Borel mass $M^2 \sim 1$ GeV$^2$.Comment: 19 pages including two postscript figures, substantially revise

Rotational symmetry and degeneracy: a cotangent-perturbed rigid rotator of unperturbed level multiplicity

We predict level degeneracy of the rotational type in diatomic molecules described by means of a cotangent-hindered rigid rotator. The problem is shown to be exactly solvable in terms of non-classical Romanovski polynomials. The energies of such a system are linear combinations of t(t+1) and 1/[t(t+1)+1/4] terms with the non-negative integer principal quantum number t=n+|/bar{m}| being the sum of the degree n of the polynomials and the absolute value, |/bar{m}|, of the square root of the separation constant between the polar and azimuthal motions. The latter obeys, with respect to t, the same branching rule, |/bar{m}|=0,1,..., t, as does the magnetic quantum number with respect to the angular momentum, l, and, in this fashion, the t quantum number presents itself indistinguishable from l. In effect, the spectrum of the hindered rotator has the same (2t+1)-fold level multiplicity as the unperturbed one. For small t values, the wave functions and excitation energies of the perturbed rotator differ from the ordinary spherical harmonics, and the l(l+1) law, respectively, while approaching them asymptotically with increasing t. In this fashion the breaking of the rotational symmetry at the level of the representation functions is opaqued by the level degeneracy. The model provides a tool for the description of rotational bands with anomalously large gaps between the ground state and its first excitation.Comment: 10 pages, 6 figures; Molecular Physics 201

Meson-baryon couplings and the F/DF/D ratio from QCD sum rules

Motivated by the recent work on the calculation of the $\pi NN$ coupling constant using QCD sum rule beyond the chiral limit, we construct the corresponding sum rules for the couplings, $\eta NN$, $\pi \Xi\Xi$, $\eta \Xi\Xi$, $\pi \Sigma \Sigma$ and $\eta \Sigma \Sigma$. In constructing the $\eta$-baryon sum rules, we use the second moment of the $\eta$ wave function, which we obtain from the pion wave function after SU(3) rotation. In the SU(3) symmetric limit, we can identify the term responsible for the $F/D$ ratio in the OPE, which after the sum rule analysis gives $F/D\sim 0.2$, a factor of 3 smaller than from other studies. We also present a qualitative analysis including the SU(3) breaking terms.Comment: 24 pages including 6 figures, slightly revised, to appear in Nuclear Physics

Pion weak decay constant at finite density from the instanton vacuum

We investigate the pion weak decay constant (F_pi) and pion mass (m_pi) at finite density within the framework of the nonlocal chiral quark model from the instanton vacuum with the finite quark-number chemical potential (mu) taken into account. We mainly focus on the Nambu-Goldstone phase below the critical value of the chemical potential mu_c ~ 320 MeV, which is determined consistently within the present framework. The breakdown of Lorentz invariance at finite density being considered, the time (F^t_pi) and space (F^s_pi) components are computed separately, and the corresponding results turn out to be: F^t_pi = 82.96 MeV and F^s_pi = 80.29 MeV at mu_c, respectively. Using the in-medium Gell-Mann-Oakes-Renner (GOR) relation, we show that the pion mass increases by about 15% at mu_c.Comment: 12 pages, 4 figures, accepted for publicaion in Phys.Lett.

Strange form factors of the proton: a new analysis of the neutrino (antineutrino) data of the BNL-734 experiment

We consider ratios of elastic neutrino(antineutrino)-proton cross sections measured by the Brookhaven BNL-734 experiment and use them to obtain the neutral current (NC) over charged current (CC) neutrino-antineutrino asymmetry. We discuss the sensitivity of these ratios and of the asymmetry to the electric, magnetic and axial strange form factors of the nucleon and to the axial cutoff mass M_A. We show that the effects of the nuclear structure and interactions on the asymmetry and, in general, on ratios of cross sections are negligible. We find some restrictions on the possible values of the parameters characterizing the strange form factors. We show that a precise measurement of the neutrino-antineutrino asymmetry would allow the extraction of the axial and vector magnetic strange form factors in a model independent way. The neutrino-antineutrino asymmetry turns out to be almost independent on the electric strange form factor and on the axial cutoff mass.Comment: 12 page