124658034
Field-theoretical space-time position operator
A field-theoretical space-time position operator can be properly defined for the Dirac field, the Klein-Gordon field and the photon field, where its temporal component can also represent an observable according to the formalism of POVMs. To achieve this, the 6×1 spinor representation of the photon field and the Feshbach-Villars representation of the Klein-Gordon field are used. Such a space-time position operator plays the role of a generalized Noether charge associated with a local U(1) symmetry, and its second-quantized form shows that quantum fields possess zero-point times, which implies that a zero-point fluctuation of energy must be accompanied with a zero-point fluctuation of time, and then in agreement with the time-energy uncertainty principle. In practice, some possible physical effects associated with the presence of zero-point times, remain to be found. PACS numbers: 03.65.Pm, 03.70.+k
117918704
Some new insights on the statistical origin of the Bekenstein-Hawking entropy I: Some heuristic arguments
Now that the Bekenstein-Hawking entropy has been found within the traditional theory, its physical interpretation should hide in quantum field theory in curved spacetime (only its quantum corrections require a detailed knowledge of quantum gravity). However, to interpret the statistical origin of the Bekenstein-Hawking entropy, there have developed many microscopic pictures, some of them are based on the theories that themselves remain to be experimentally verified, while some cite the Hawking temperature formula and actually argue in circle (and then they have not provided more information than the seminal work of Bekenstein and Hawking). Within quantum field theory in curved spacetime (without introducing any new hypothesis), it is inevitable for us to attribute the Bekenstein-Hawking entropy to entanglement entropy. In the first part we just provide a heuristic argument, a rigorous theoretical model will be presented in our next work.
119791200
Zero-Point Time of Quantum Fields
Based on the first principles and without resorting to any additional assumption, a new physical quantity describing the space-time position of particle-number center of quantum fields is introduced, which can be regarded as a generalized Noether charge related to the symmetry under a local gauge transformation. As an interesting result, one can show that quantum fields have a zero-point time, which is related to the zero-point energy of quantum fields via the Heisenberg uncertainty principle.
120913481
Zitterbewegung in quantum field theory
Traditionally, the zitterbewegung (ZB) of the Dirac electron has just been studied at the level of quantum mechanics. Seeing the fact that an old interest in ZB has recently been rekindled by the investigations on spintronic, graphene, and superconducting systems, etc., this paper presents a quantum-field-theory investigation on ZB and obtains the conclusion that, the ZB of an electron arises from the influence of virtual electron-positron pairs (or vacuum fluctuations) on the electron.
119073212
Relativistic free-motion time-of-arrival
Relativistic free-motion time-of-arrival theory for massive spin-1/2 particles is systematically developed. Contrary to the nonrelativistic time-of-arrival operator studied thoroughly in the previous literatures, the relativistic time-of-arrival operator possesses self-adjoint extensions because of the particle–antiparticle symmetry. The nonrelativistic limit of our theory is in agreement with the nonrelativistic time-of-arrival theory.
118394364
Zitterbewegung and its significance for the Hawking radiation
The Hawking radiation can be viewed from very different perspectives, not all of which can be proved to be rigorously equivalent to one another. On the other hand, an old interest in the zitterbewegung (ZB) of the Dirac electron has recently been rekindled by the investigations on spintronics and graphene, etc. In this letter, we show that, if particles emitted by black holes are electrons or positrons, one can also regard the Hawking radiation as a ZB process.
17015371
Analysis of the X(1576) as a tetraquark state with the QCD sum rules
In this letter, we take the point of view that the X(1576) be tetraquark state which consists of a scalar-diquark and an anti-scalar-diquark in relative P -wave, and calculate its mass in the framework of the QCD sum rules approach. The numerical value of the mass mX = (1.66±0.14)GeV is consistent with the experimental data, there may be some tetraquark component in the vector meson X(1576). PACS numbers: 12.38.Lg; 12.39.Mk
121984241
Representation of the propagator and Schwinger functions of Dirac fields in terms of Brownian motions
A mathematical path integral representation of the propagator and Schwinger functions of the Dirac fields on R4 interacting with a smooth non‐Abelian gauge field is presented. The representation is essentially in terms of expectations with respect to the Brownian motion on R4.
108637108
The construction and space qualification of the control electronics for the tracker detector cooling system of the AMS-02 experiment
Abstract This article describes the control electronics for the silicon tracker cooling system in the AMS-02 apparatus. It also contains a brief description of the cooling system itself necessary for the description of the electronics. The tracker cooling system includes a set of various sensors and actuators which are necessary for bringing the tracker detector to a uniform temperature at which it can operate correctly. In order to test the system performing the various qualification activities we have built also an Electronic Ground support equipment (EGSE). The EGSE should simulate the behaviour of all sensors and actuators previously mentioned.
121663887
Mass and transverse momentum dependence of the dielectron yield in p-Be collisions at 4.9 GeV
We present the invariant mass and transverse momentum dependence of direct electron-positron pair production in {ital p}-Be collisions at a beam kinetic energy of 4.9 GeV. The acceptance of our apparatus is shown to have no significant effect for masses above 0.15 GeV. After a correction is made for the available phase space, the transverse momentum dependence of the data is found to be comparable to hadron-hadron observations. A phenomenological calculation involving {pi}{sup +}{pi}{sup {minus}} annihilation into {ital e}{sup +}e{sup {minus}} is shown to be in good agreement with our measurements.
54896614
Galois conjugates of topological phases
Galois conjugation relates unitary conformal field theories and topological quantum field theories (TQFTs) to their nonunitary counterparts. Here we investigate Galois conjugates of quantum double models, such as the Levin-Wen model. While these Galois-conjugated Hamiltonians are typically non-Hermitian, we find that their ground-state wave functions still obey a generalized version of the usual code property (local operators do not act on the ground-state manifold) and hence enjoy a generalized topological protection. The key question addressed in this paper is whether such nonunitary topological phases can also appear as the ground states of Hermitian Hamiltonians. Specific attempts at constructing Hermitian Hamiltonians with these ground states lead to a loss of the code property and topological protection of the degenerate ground states. Beyond this, we rigorously prove that no local change of basis can transform the ground states of the Galois-conjugated doubled Fibonacci theory into the ground states of a topological model whose Hermitian Hamiltonian satisfies Lieb-Robinson bounds. These include all gapped local or quasilocal Hamiltonians. A similar statement holds for many other nonunitary TQFTs. One consequence is that these nonunitary TQFTs do not describe physical realizations of topological phases. In particular, this implies that the ``Gaffnian'' wave function can not be the ground state of a gapped fractional quantum Hall state.