54545936
Multirefringence phenomena in nonlinear electrodynamics
Universite´ de Nice Sophia Antipolis, 06103 Nice Cedex 2, Franceand Dipartimento di Fisica and ICRA, Sapienza Universita` di Roma, I-00185 Rome, Italy(Received 19 April 2013; published 13 September 2013)Wave propagation in nonlinear theories of the electromagnetism described by Lagrangian densitiesdependent upon its two local invariants LðF;GÞ is revisited. On the light of the recent ﬁndings inmetamaterials, it is here shown that trirefringence is also a possible phenomenon to occur in the realm ofsuch nonlinear theories. A speciﬁc model exhibiting this effect is investigated in terms of both phase andgroup velocities. It is claimed that wave propagation in some well known nonlinear models for spin-oneﬁelds, like QED and QCD in certain regimes, may exhibit trirefringence.
118901774
Gluon Shadowing and Hadron Production at RHIC
Nuclear Science Division, Mailstop 70-319, Lawrence Berkeley Laboratory, Berkeley, California 94720.(October 3,2001)Hadron multiplicity in the central rapidity region of high-energy heavy-ion collisions is investi-gated within a two-component mini-jet model which consists of soft and semi-hard particle produc-tion. The hard contribution from mini-jets is reevaluated using the latest parameterization of partondistributions and nuclear shadowing. The energy dependence of the experimental data from RHICrequires a strong nuclear shadowing of the gluon distribution in this model. The centrality depen-dence of the hadron multiplicity at√s = 130 GeV is reproduced well with the impact-parameterdependent parton shadowing. However, energy variation of the centrality dependence is needed todistinguish diﬀerent particle production mechanisms such as the parton saturation model.25.75.-q,12.38.Bx,12.38.Mh,24.85.+p
189809274
Dirac structure of quark-hadron vertex in Bethe-Salpeter wave function under the framework covariant instantaneous ansatz
In the framework of covariant instantaneous ansatz, the general form of the quark-hadron vertex of certain kind of mesons is provided; how to arrange the Dirac covariants of the complete set by the power counting rule is discussed. Employing the leading order Dirac covariants for vector and pseudoscalar mesons, their decay constants are calculated. This proceeding paper is complementary to our other two previous papers, emphasizing on some conceptual discussions. The strong interaction is special for its basic degree of freedoms are confined in hadrons, preventing the measurement of the “really-free” quanta, i.e., quarks and gluons in quantum chromodynamics (QCD). Hence, a description for the asymptotic states, the hadrons, in the strong interactions/collisions, with the language of the basic quanta/fields, quarks, and gluons, is a necessary but challenging task. In the framework of relativistic quantum field theory, at least one “standard” way to describe bound states, i.e., the Bethe-Salpeter wave function (BSW), which is the solution of the Bethe-Salpeter integral equation (BSE), seems available. Through an extensive employment of various techniques in the quantum field theory, such as the DysonSchwinger Equations, one may expect to know the movement of the quarks and gluons in hadrons, and to calculate various kinds of interactions/collisions in various energy scales with such knowledge. This is one of the most important purposes of studying the hadron structure. However, a full understanding of the physical picture of the BSW and a satisfactory way to solve the BES in QCD are still beyond approach. Even, one is not able to give the “rigorous” form of the kernel of the BSE without practical non-perturbative techniques in QCD. More specifically, one has a very powerful picture/tool in high energy hadronic interactions, i.e., the perturbative QCD inspired parton model, but how to approach this parton picture starting from low energy BSW of hadron is an open question. At the same time, the standard factorization scheme is often facing danger in various special processes [1, 2]. So it is very much justified to put more labour on the study of BSW/BSE, especially their
13962394
Combination of Heavy Quark with Partons from Quark-Gluon Matter: a Scaling Probe
In relativistic heavy ion collisions, the cross section of heavy hadron production via the combination of a heavy quark with a light one from the quark-gluon matter can be factorized. It is the convolution of twist-4 combination matrix elements, the parameters corresponding to the parton distributions of the quark-gluon matter, as well as the hard partonic cross section of heavy quark production calculable in PQCD. These parton distributions and combination matrix elements are functions of a scaling variable which is the momentum fraction of the heavy quark w.r.t. the heavy hadron. In the same factorization framework, the combination matrix elements appear in other `simpler' processes and can be extracted. Taking them as inputs, comparing with data from RHIC and (future) LHC, we can get the parton distributions of the quark-gluon matter just as the similar way we get those of nucleon, pion, or photon, etc..
123786527
Decay constants fp of unequal-mass pseudoscalar mesons in a Bethe-Salpeter framework using a generalized structure of hadron-quark vertex function
115465221
OPERA Collaboration have observed phase speed of neutrino wave function, while advanced time displacement is mainly due to finite life time of pion
First we call the attention that velocity defined by ratio between some intervals of space and time respectively is sometimes ambiguous, in the framework of quantum theory. Velocity in general is not possible to be well defined as some generator of certain space-time symmetry operation. Then in section 3 by analyzing the OPERA experiment we show that the OPERA Collaboration may have measured the phase speed of the neutrino wave function. Employing a very (maybe too) simple model which is just a reproduction from Brillouin's classical book, we demonstrate the phase velocity and group velocity. These are just a qualitative illustration rather than aiming to quantitively explain the OPERA data. However, how to rigorously define the phase containing the particle production ordering information as a space-time distribution observable in QFT needs more investigations. Due to the finite life time of the pions (w.r.t. its flying time in the 1 km long tunnel) which decay to the muon neutrinos, the wave form for neutrinos recorded by OPERA is deformed from that of the proton. Such an effect is estimated to lead to an advanced time displacement of the order of 100ns, which coincides with the measured. Such an effect can only be significant when measuring phase speed and the recorded neutrino events per extraction of proton smaller than one, as the OPERA case.
119087982
Inhomogeneous reheating scenario with DBI fields
We discuss a new mechanism which can be responsible for the origin of the primordial perturbation in inflationary models, the inhomogeneous DBI reheating scenario. Light DBI fields fluctuate during inflation, and finally create the density perturbations through modulation of the inflation decay rate. In this note, we investigate the curvature perturbation and its non-Gaussianity from this new mechanism. Presenting generalized expressions for them, we show that the curvature perturbation not only depends on the particular process of decay but is also dependent on the sound speed cs from the DBI action. More interestingly we find that the non-Gaussianity parameter fNL is independent of cs. As an application we exemplify some decay processes which give a viable and detectable non-Gaussianity. Finally we find a possible connection between our model and the DBI-Curvaton mechanism.
118396850
SO(4) monopole as a new topological invariant and its topological structure
By making use of the decomposition theory of gauge potential, the inner structure of SU(2) and SO(4) gauge theory is discussed in detail. We find the SO(4) monopole can be given via projecting the SO(4) gauge field onto an antisymmetric tensor. This projection fix the coset $% SU(2)/U(1)\bigotimes SU(2)/U(1)$ of SO(4) gauge group. The generalized Hopf map is given via a Dirac spinor. Further we prove that this monopole can be consider as a new topological invariant. Which is composed of two monopole structures. Local topological structure of the SO(4) monopole is discussed in detail, which is quantized by winding number. The Hopf indices and Brouwer degree labels the local property of the monopoles.
14118127
The Bifurcation of the Topological Structure in the Sunspot's Electric Topological Current with Locally Gauge-invariant Maxwell-Chern-Simons Term
The topological structure of the electric topological current of the locally gauge invariant Maxwell-Chern-Simons Model and its bifurcation is studied. The electric topological charge is quantized in term of winding number. The Hopf indices and Brouwer degree labeled the local topological structure of the electric topological current. Using Φ-mapping method and implicit function theory, the electric topological current is found generating or annihilating at the limit points and splitting or merging at the bifurcate points. The total electric charge holds invariant during the evolution.
118068874
Topological Defects in 3-d Euclidean Gravity
By making use of the complete decomposition of SO(3) spin connection, the topological defect in 3-dimensional Euclidean gravity is studied in detail. The topological structure of disclination is given as the combination of a monopole structure and a vortex structure. Furthermore, the Kac-Moody algebra generated by the monopole and vortex is discussed in three dimensional Chern-Simons theory.
118740978
Constraints on Randall-Sundrum model from the events of dijet production with QCD next-to-leading order accuracy at the LHC
We study the dijet production in Randall-Sundrum model at the LHC with QCD next-to-leading(NLO) order accuracy. Our results show that the QCD NLO corrections can increase the total cross sections by more than $80\%$ and reduce the scale dependence. We also explore in detail several important kinematic distributions at the NLO level. Moreover, we discuss the upper limits of the KK graviton excluded mass range and the allowed parameter space for the coupling constant and KK graviton mass, using the experiment data.