We determine the light meson spectrum in QCD in the presence of background magnetic fields using quenched Wilson fermions. Our continuum extrapolated results indicate a monotonous reduction of the ...connected neutral pion mass as the magnetic field grows. The vector meson mass is found to remain nonzero, a finding relevant for the conjectured ρ-meson condensation at strong magnetic fields. The continuum extrapolation was facilitated by adding a novel magnetic field–dependent improvement term to the additive quark mass renormalization. Without this term, sizable lattice artifacts that would deceptively indicate an unphysical rise of the connected neutral pion mass for strong magnetic fields are present. We also investigate the impact of these lattice artifacts on further observables like magnetic polarizabilities and discuss the magnetic field–induced mixing between ρ-mesons and pions. We also derive Ward-Takashi identities for QCD+QED both in the continuum formulation and for (order a–improved) Wilson fermions.
A
bstract
We determine the equation of state of 2+1-flavor QCD with physical quark masses, in the presence of a constant (electro)magnetic background field on the lattice. To determine the free ...energy at nonzero magnetic fields we develop a new method, which is based on an integral over the quark masses up to asymptotically large values where the effect of the magnetic field can be neglected. The method is compared to other approaches in the literature and found to be advantageous for the determination of the equation of state up to large magnetic fields. Thermodynamic observables including the longitudinal and transverse pressure, magnetization, energy density, entropy density and interaction measure are presented for a wide range of temperatures and magnetic fields, and provided in ancillary files. The behavior of these observables confirms our previous result that the transition temperature is reduced by the magnetic field. We calculate the magnetic susceptibility and permeability, verifying that the thermal QCD medium is paramagnetic around and above the transition temperature, while we also find evidence for weak diamagnetism at low temperatures.
A
bstract
The effect of an external (electro)magnetic field on the finite temperature transition of QCD is studied. We generate configurations at various values of the quantized magnetic flux with
N
...f
= 2 + 1 flavors of stout smeared staggered quarks, with physical masses. Thermodynamic observables including the chiral condensate and susceptibility, and the strange quark number susceptibility are measured as functions of the field strength. We perform the renormalization of the studied observables and extrapolate the results to the continuum limit using
N
t
= 6
,
8 and 10 lattices. We also check for finite volume effects using various lattice volumes. We find from all of our observables that the transition temperature
T
c
significantly decreases with increasing magnetic field. This is in conflict with various model calculations that predict an increasing
T
c
(
B
). From a finite volume scaling analysis we find that the analytic crossover that is present at
B
= 0 persists up to our largest magnetic fields
eB
≈ 1 GeV
2
, and that the transition strength increases mildly up to this
eB
≈ 1 GeV
2
.
A
bstract
We study the influence of strong external magnetic fields on gluonic and fermionic observables in the QCD vacuum at zero and nonzero temperatures, via lattice simulations with
N
f
= 1 + 1 ...+ 1 staggered quarks of physical masses. The gluonic action density is found to undergo magnetic catalysis at low temperatures and inverse magnetic catalysis near and above the transition temperature, similar to the quark condensate. Moreover, the gluonic action develops an anisotropy: the chromo-magnetic field parallel to the external field is enhanced, while the chromo-electric field in this direction is suppressed. We demonstrate that the same hierarchy is obtained using the Euler-Heisenberg effective action. Conversely, the topological charge density correlator does not reveal a significant anisotropy up to magnetic fields
eB
≈ 1 GeV
2
. Furthermore, we show that the pressure remains isotropic even for nonzero magnetic fields, if it is defined through a compression of the system at fixed external field. In contrast, if the flux of the field is kept fixed during the compression — which is the situation realized in the lattice simulation — the pressure develops an anisotropy. We estimate the quark and gluonic contributions to this anisotropy, and relate them to the magnetization of the QCD vacuum. After performing electric charge renormalization, we obtain an estimate for the magnetization, which indicates that QCD is paramagnetic.
Paramagnetic squeezing of QCD matter Bali, G S; Bruckmann, F; Endrődi, G ...
Physical review letters,
2014-Jan-31, Letnik:
112, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We determine the magnetization of quantum chromodynamics for several temperatures around and above the transition between the hadronic and the quark-gluon phases of strongly interacting matter. We ...obtain a paramagnetic response that increases in strength with the temperature. We argue that due to this paramagnetism, chunks of quark-gluon plasma produced in noncentral heavy ion collisions should become squeezed perpendicular to the magnetic field. This anisotropy will then contribute to the elliptic flow v2 observed in such collisions, in addition to the pressure gradient that is usually taken into account. We present a simple estimate for the magnitude of this new effect and a rough comparison to the effect due to the initial collision geometry. We conclude that the paramagnetic effect might have a significant impact on the value of v2.
Weak Decay of Magnetized Pions Bali, G S; Brandt, B B; Endrődi, G ...
Physical review letters,
2018-Aug-17, Letnik:
121, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The leptonic decay of charged pions is investigated in the presence of background magnetic fields. In this situation, Lorentz symmetry is broken, and new fundamental decay constants need to be ...introduced, associated with the decay via the vector part of the electroweak current. We calculate the magnetic field dependence of both the usual and a new decay constant nonperturbatively on the lattice. We employ both Wilson and staggered quarks and extrapolate the results to the continuum limit. With this nonperturbative input, we calculate the tree level electroweak amplitude for the full decay rate in strong magnetic fields. We find that the muonic decay of the charged pion is enhanced drastically by the magnetic field. We comment on possible astrophysical implications.
We present the nonperturbative computation of renormalization factors in the RI'−(S)MOM (regularization independent (symmetric) momentum subtraction) schemes for the QCD gauge field ensembles ...generated by the CLS (coordinated lattice simulations) effort with three flavors of nonperturbatively improved Wilson (clover) quarks. We use ensembles with the standard (anti-)periodic boundary conditions in the time direction as well as gauge field configurations with open boundary conditions. Besides flavor-nonsinglet quark-antiquark operators with up to two derivatives we also consider three-quark operators with up to one derivative. For the RI′−SMOM scheme results we make use of the recently calculated three-loop conversion factors to the ¯ MS scheme.
Introduction: To compare the intubating conditions at 60 seconds between 4*ED95 dose of cisatracurium and 2*ED95 dose of cisatracurium in combination with priming and low dose ketamine Primary ...Objective: jaw relaxation for laryngoscopy, vocal cord position on laryngoscopy, and coughing or bucking response to intubation. Secondary Objective: To compare the hemodynamic changes up 10 minutes after intubation in the two groups. In this prospective study, a total of 68 patients were undergoing general anesthesia for surgery with placement of endotracheal tube placement. Patients will be divided into two groups comprising 34 patients each. The patients were allocated one of the two groups by computerized randomization. *Group A received bolus dose of cisatracurium which is 0.2 mg/kg (4*ED95). **Group B received cisatracurium in dose of 0.1 mg/kg (2*ED95) with priming (which is 10% of the bolus dose) and low dose ketamine of about 0.5 mg/kg. It was possible to achieve acceptable laryngoscopy and intubating condition in both the groups within 90 seconds. When grades of laryngoscopy and ease of intubation were compared, 2*ED95 dose along with priming plus low dose ketamine produced superior results than 4*ED95 group. When the mean arterial pressure and pulse rate were compared between the two groups, it was observed that mean arterial pressure and pulse rate were only slightly higher in the 2*ED95 along with priming and ketamine.
A
bstract
We study local CP-violation on the lattice by measuring the local correlation between the topological charge density and the electric dipole moment of quarks, induced by a constant external ...magnetic field. This correlator is found to increase linearly with the external field, with the coefficient of proportionality depending only weakly on temperature. Results are obtained on lattices with various spacings, and are extrapolated to the continuum limit after the renormalization of the observables is carried out. This renormalization utilizes the gradient flow for the quark and gluon fields. Our findings suggest that the strength of local CP-violation in QCD with physical quark masses is about an order of magnitude smaller than a model prediction based on nearly massless quarks in domains of constant gluon backgrounds with topological charge. We also show numerical evidence that the observed local CP-violation correlates with spatially extended electric dipole structures in the QCD vacuum.
Slope failures in a mining project will contribute to significant safety impacts and economic losses. Therefore, it is imperative for mining engineers to analyse and design an open pit mine ...considering safety purposes. In this study, a limit equilibrium method using GeoSlope-Slope/W program was used to investigate the stability of an open pit mining slope for a proposed mining activity based on a case study in Tanjung Enim, District of Muara Enim, Province of South Sumatera - Indonesia. The results of this study reveal that the slope design for the proposed mining activity is technically not in stable condition due to the shear force of the slope is higher than its shear strength. Such mechanism occurs due to the existence of a complex geotechnical condition beneath the surface, such as faults and discontinuities, which then lead to the reduction of slope strength. Having an inapplicable proposed slope design, this study proposes a re-design of slope for safety purposes in order to support the future mining operation. The analysis approach proposed in this study can be a viable alternative to assess the stability of slopes in any mining operation when a complex geotechnical condition exists.
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