Kink mass quantum shifts from SUSY quantum mechanics

In this paper a new version of the DHN (Dashen–Hasslacher–Neveu) formula, which is used to compute the one-loop order kink mass correction in (1+1)-dimensional scalar field theory models, is constructed. The new expression is written in terms of the spectral data coming from the supersymmetric partner operator of the second-order small kink fluctuation operator and allows us to compute the kink mass quantum shift in new models for which this calculation was out of reach by means of the old formula.     

One-loop approximation of Møller scattering in generalized Krein-space quantization

It has been shown that the negative-norm states necessarily appear in a covariant quantization of the free minimally coupled scalar field in de Sitter spacetime. In this processes ultraviolet and infrared divergences have been automatically eliminated. A natural renormalization of the one-loop interacting quantum field in Minkowski spacetime (λφ ⁴) has been achieved through the consideration of the negative-norm states defined in Krein space. It has been shown that the combination of quantum field theory in Krein space together with consideration of quantum metric fluctuation, results in quantum field theory without any divergences. Pursuing this approach, we express Wick’s theorem and calculate Møller scattering in the one-loop approximation in generalized Krein space. The mathematical consequence of this method is the disappearance of the ultraviolet divergence in the one-loop approximation.     

Quaternionic Kähler metrics associated with special Kähler manifolds

We give an explicit formula for the quaternionic Kähler metrics obtained by the HK/QK correspondence. As an application, we give a new proof of the fact that the Ferrara–Sabharwal metric as well as its one-loop deformation is quaternionic Kähler. A similar explicit formula is given for the analogous (K/K) correspondence between Kähler manifolds endowed with a Hamiltonian Killing vector field. As an example, we apply this formula in the case of an arbitrary conical Kähler manifold.     

Perturbative quantum gravity in analogy with Fermi theory of weak interactions using bosonic tensor fields

In this paper we work in perturbative quantum gravity and we introduce a new effective model for gravity. Expanding the Einstein–Hilbert Lagrangian in graviton field powers we have an infinite number of terms. In this paper we study the possibility of an interpretation of more than three graviton interacting vertices as effective vertices of a most fundamental theory that contain tensor fields. Here we introduce a Lagrangian model named I.T.B. (intermediate-tensor-boson) where four gravitational pseudo-currents that contain two gravitons couple to three massive tensorial fields of ranks one, three and five, respectively. We show that the exchange of those massive particles reproduces, at low energy, the interacting vertices for four or more gravitons. In a particular version, the model contains a dimensionless coupling constant g and the mass M of the intermediate bosons as free parameters. The universal gravitational constant G_N is shown to be proportional to the inverse of mass squared of mediator fields, particularly . A foresighting choice of the dimensionless coupling constant could lower the energy scale where quantum gravity aspects show up.     

Cosmological Acceleration from Virtual Gravitons

Intrinsic properties of the space itself and quantum fluctuations of its geometry are sufficient to provide a mechanism for the acceleration of cosmological expansion (dark energy effect). Applying Bogoliubov–Born–Green–Kirkwood–Yvon hierarchy approach to self-consistent equations of one-loop quantum gravity, we found exact solutions that yield acceleration. The permanent creation and annihilation of virtual gravitons is not in exact balance because of the expansion of the Universe. The excess energy comes from the spontaneous process of graviton creation and is trapped by the background. It provides the macroscopic quantum effect of cosmic acceleration.     

Kℓ3 decay in quantum field theory with chiral symmetry

In quantum chiral field theory the form factor of K_?3 decay is calculated in the one-loop approximation. The results obtained are in good agreement with the recent experimental data.     

Evaporation of near-extremal Reissner-Nordström black holes

The formation of near-extremal Reissner-Nordstr?m black holes in the S-wave approximation can be described, near the event horizon, by an effective solvable model. The corresponding one-loop quantum theory remains solvable and allows one to follow analytically the evaporation process, which is shown to require an infinite amount of time.     

Constant gauge fields and their quantum fluctuations

We analyze the vacuum fluctuations generated by translation-invariant gauge fields and show that these fields are unstable unless they are (anti-)self-dual and abelian. Self-dual constant fields support infinitely many zero modes analogous to instantons. The quantum corrections to the classical action are worked out in the one-loop approximation.     

Quantum fluctuations and lattice dimerization in coupled polymer chains

Effects of quantum lattice fluctuations on the Peierls dimerization are considered for two neighboring polymer chains, which are modeled individually by the Su, Schrieffer, and Heeger Hamiltonian and coupled by an interchain electron-transfer term. By a functional-integral approach, an equation for the dimerization order parameter is obtained within a one-loop approximation. It is found that the quantum fluctuations are partly suppressed by the interchain coupling and then the system is dimerized for an arbitrary coupling constant and phonon frequency even for the spinless fermion system.     

Gauge-Invariant and Gauge-Fixing Independent Effective Action in One-Loop Quantum Gravity

The one-parameter dependent family of the gauge invariant and gauge fixing independent effective actions is considered in one-loop approximation. The one-loop unique effective action (chosing as the representative of this family) in d = 4 Einstein quantum gravity with scalar field and Brans-Dicke quantum theory in flat space, in d = 4 Einstein gravity on De Sitter background, in higher derivative gravity on d-dimensional torus compactified background is calculated. The configuration-space metric dependence of the unique effective action in these calculations is investigated. The appearing problems (the configuration-space metric dependence of the physical quantities like induced gravitational constant) are discussed.     

Renormalization of N = 2, 4 Yang-Mills theories with soft breaking of an extended supersymmetry by N = 1 mass term

N = 2, 4 Yang-Mills theories with soft breaking of an extended supersymmetry by mass terms are considered. It is proved that for N = 4 there are no ultraviolet divergences in the mass renormalization constants to all orders of perturbation theory. For N = 2 our two-loop calculations show that the charge and mass renormalization constants contain only one-loop divergences and are the same in this order. It is shown by direct calculation that mass terms can acquire finite quantum corrections starting from the two-loop approximation. The renormalization scheme dependence of N = 4 renormalization group functions is investigated. We have found that unlike renormalization schemes with minimal subtractions of divergences other renormalization schemes give a nonzero β-function. At nonzero masses the β-function in MOM schemes is not zero even at the one-loop level. In the massless case β≠0 beginning from the two-loop approximation.     

Quantum critical behaviour of a disordered granular superconductor with charging effects

The effect of quantum fluctuations of the phase on the low-temperature critical behaviour of a three-dimensional disordered (site-diluted) granular superconductor with Coulomb interactions is studied using the renormalization group method. In the one-loop approximation the system exhibits a focus-type stable fixed point which gives rise to unusual critical behaviour with oscillating corrections to the scaling.     

Eikonal Approximation to 5D Wave Equations and the 4D Space-Time Metric

We apply a method analogous to the eikonal approximation to the Maxwell wave equations in an inhomogeneous anisotropic medium and geodesic motion in a three dimensional Riemannian manifold, using a method which identifies the symplectic structure of the corresponding mechanics, to the five dimensional generalization of Maxwell theory required by the gauge invariance of Stueckelberg's covariant classical and quantum dynamics. In this way, we demonstrate, in the eikonal approximation, the existence of geodesic motion for the flow of mass in a four dimensional pseudo-Riemannian manifold. These results provide a foundation for the geometrical optics of the five dimensional radiation theory and establish a model in which there is mass flow along geodesics. We then discuss the interesting case of relativistic quantum theory in an anisotropic medium as well. In this case the eikonal approximation to the relativistic quantum mechanical current coincides with the geodesic flow governed by the pseudo-Riemannian metric obtained from the eikonal approximation to solutions of the Stueckelberg–Schrödinger equation. The locally symplectic structure which emerges is that of a generally covariant form of Stueckelberg's mechanics on this manifold.     

Quantum correlation dynamics in photosynthetic processes assisted by molecular vibrations

During the long course of evolution, nature has learnt how to exploit quantum effects. In fact, recent experiments reveal the existence of quantum processes whose coherence extends over unexpectedly long time and space ranges. In particular, photosynthetic processes in light-harvesting complexes display a typical oscillatory dynamics ascribed to quantum coherence. Here, we consider the simple model where a dimer made of two chromophores is strongly coupled with a quasi-resonant vibrational mode. We observe the occurrence of wide oscillations of genuine quantum correlations, between electronic excitations and the environment, represented by vibrational bosonic modes. Such a quantum dynamics has been unveiled through the calculation of the negativity of entanglement and the discord, indicators widely used in quantum information for quantifying the resources needed to realize quantum technologies. We also discuss the possibility of approximating additional weakly-coupled off-resonant vibrational modes, simulating the disturbances induced by the rest of the environment, by a single vibrational mode. Within this approximation, one can show that the off-resonant bath behaves like a classical source of noise.     

Approximation of quantum assemblages

In this paper, we derive a set of projectors on a large Hilbert space which can universally work for approximating quantum assemblages with binary inputs and outputs. The dimension of the Hilbert space depends on the accuracy of the approximation.     

Quantum fluctuations in the one-instanton sector of the CPn−1 model

Within the two-dimensional CP^n?1 model we calculate the instanton density function in the dilute-gas limit by studying the quantum fluctuations in the one-instanton sector in the one-loop approximation. The result disagrees with the $\text{1}\text{n}$ expansion. Green functions in the one-instanton background are displayed.     

Quantum geometrodynamics: whence,whither?

Quantum geometrodynamics is canonical quantum gravity with the three-metric as the configuration variable. Its central equation is the Wheeler–DeWitt equation. Here I give an overview of the status of this approach. The issues discussed include the problem of time, the relation to the covariant theory, the semiclassical approximation as well as applications to black holes and cosmology. I conclude that quantum geometrodynamics is still a viable approach and provides insights into both the conceptual and technical aspects of quantum gravity.

These considerations reveal that the concepts of spacetime and time itself are not primary but secondary ideas in the structure of physical theory. These concepts are valid in the classical approximation. However, they have neither meaning nor application under circumstances when quantum-geometrodynamical effects become important. ...There is no spacetime, there is no time, there is no before, there is no after. The question what happens “next” is without meaning [1].

Dedicated to the memory of John Archibald Wheeler.     

Quantum correlations of helicity entangled states in non-inertial frames beyond single mode approximation

A helicity entangled tripartite state is considered in which the degree of entanglement is preserved in non-inertial frames. It is shown that Quantum Entanglement remains observer independent. As another measure of quantum correlation, Quantum Discord has been investigated. It is explicitly shown that acceleration has no effect on the degree of quantum correlation for the bipartite and tripartite helicity entangled states. Geometric Quantum Discord as a Hilbert–Schmidt distance is computed for helicity entangled states. It is shown that living in non-inertial frames does not make any influence on this distance, either. In addition, the analysis has been extended beyond single mode approximation to show that acceleration does not have any impact on the quantum features in the limit beyond the single mode. As an interesting result, while the density matrix depends on the right and left Unruh modes, the Negativity as a measure of Quantum Entanglement remains constant. Also, Quantum Discord does not change beyond single mode approximation.     

量子孤子在光纤中的传播特性

利用线性近似和分步傅里叶变换法，分析了量子孤子在无耗光纤中的传播规律.量子孤子在光纤中的行为由量子非线性薛定谔方程（QNSE）描述,用线性近似法求解此方程，将量子噪声与经典部分分离，着重讨论了孤子量子噪声的演化行为，分析了高阶色散对噪声压缩的影响.结果表明：在较短的传输距离内，孤子的压缩性依然存在，但无论初始时压缩参数如何，随着传输距离的增加，压缩比会达到一个极限;在负色散区，三阶色散对压缩效应无影响.