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A ℛ "dual" transform is introduced which relates Quantum Field Theory and String regimes, both in a curved background with D-non-compact dimensions. This operation maps the characteristic length of one regime into the other (and, as a consequence, mass domains as well). The ℛ-transform is not an assumed or a priori imposed symmetry but is revealed by the QFT and String dynamics in curved backgrounds. The Hawking–Gibbons temperature and the string maximal or critical temperature are ℛ-mapped one into the other. If back reaction of quantum matter is included, Quantum Field Theory and String phases appear, and ℛ-relations between them manifest as well. These ℛ-transformations are explicitly shown in two relevant examples: Black Hole and de Sitter spacetimes.

We consider a class of models for the relativistic covariant wave packets (WPs) which can be used as asymptotically free in and out states in the quantum field theoretical formalisms for description of the neutrino flavor oscillation phenomenon. We demonstrate that the new “asymmetric” wave packet (AWP) is an appropriate alternative to the more conventional “symmetric” WPs, like the so-called relativistic Gaussian packet (RGP) widely used in the quantum field theory (QFT)-based approaches to neutrino oscillations. We show that RGP is not a particular case of AWP, although many properties of these models are almost identical in the quasistable regime. We discuss some features of AWP distinguishing it from RGP.

Motivated by the possibility of a string landscape, we re-examine tunneling of a scalar field across single/multiple barriers. Recent investigations have suggested modifications to the usual picture of false vacuum decay that leads to efficient and rapid tunneling in the landscape when certain conditions are met. This can be due to stringy effects (e.g. tunneling via the DBI action), or effects arising from the presence of multiple vacua (e.g. resonance tunneling). In this paper we discuss both DBI tunneling and resonance tunneling. We provide a QFT treatment of resonance tunneling using the Schrödinger functional approach. We also show how DBI tunneling for supercritical barriers can naturally lead to conditions suitable for resonance tunneling. We argue, using basic ideas from percolation theory, that tunneling can be rapid in a landscape where a typical vacuum has multiple decay channels, and discuss various cosmological implications. This rapidity vacuum decay can happen even if there are no resonance/DBI tunneling enhancements, solely due to the presence of a large number of decay channels. Finally, we consider various ways of circumventing a recent no-go theorem for resonance tunneling in quantum field theory.

We discuss consistency of the concept of external background in QFT. Different restrictions on magnitude of magnetic and electric fields are analyzed. The back reaction due to strong electric field is calculated and restrictions on the magnitude and duration of such a field are obtained. The problem of consistency of Dirac equation with a superstrong Coulomb field is discussed.

In recent papers,^1,2 it has been shown that the presence of negative norm states or negative frequency solutions are indispensable for a fully covariant quantization of the minimally coupled scalar field in de Sitter space. Their presence, while leaving unchanged the physical content of the theory, offers the advantage of eliminating any ultraviolet divergence in the vacuum energy² and infrared divergence in the two point function.³ We attempt here to extend this method to the interacting quantum field in Minkowski space-time. As an illustration of the procedure, we consider the λϕ⁴ theory in Minkowski space-time. The mathematical consequences of this method is the disappearance of the ultraviolet divergence to the one-loop approximation. This means, the effect of these auxiliary negative norm states is to allow an automatic renormalization of the theory in this approximation.

In this paper, we investigate novel protocols for the joint remote state preparation involving several senders and receivers. The highlight of our paper lies in two aspects. First, we focus on the distribution of information among multiple senders and receivers. Second, each receiver can simultaneously reconstruct a qubit state containing the joint information from all senders. These properties imply that our protocols may have many extensive applications in burgeoning quantum network communication. Our protocols cover a variety of class, i.e. two-to-three, N-to-three, and N-to-M. Through introducing the quantum fourier transform, the set of orthogonal basis in the M-dimensional Hilbert space is ingeniously constructed. Moreover, we present all the recovery operations in details. The success probability and the classical communication costs are also given.

Both algebraic equations $\mathrm{\text{Det}}(\widehat{p}-m)=0$ and $\mathrm{\text{Det}}(\widehat{p}+m)=0$ for $u$- and $v$- 4-spinors have solutions with $p_0=\pm E_p=\pm \sqrt{p^2+m^2}$. The same is true for higher-spin equations (or they may even have more complicated dispersion relations). Meanwhile, every book considers the equality $p_0=E_p$ for both $u$- and $v$-spinors of the $(1/2,0)\oplus (0,1/2))$ representation only, thus applying the Dirac–Feynman–Stueckelberg procedure for elimination of negative-energy solutions. The recent Ziino works (and, independently, the articles of several other authors) show that the Fock space can be doubled. We re-consider this possibility on the quantum-field level.

We discuss consistency of the concept of external background in QFT. Different restrictions on magnitude of magnetic and electric fields are analyzed. The back reaction due to strong electric field is calculated and restrictions on the magnitude and duration of such a field are obtained. The problem of consistency of Dirac equation with a superstrong Coulomb field is discussed.

We write solutions of relativistic quantum equations explicitly in the helicity basis for S = 1/2 and S = 1. We present the analyses of relations between Dirac-like and Majorana-like field operators. Several interesting features of bradyonic and tachyonic solutions are presented.

We adopt the Dirac model for graphene and calculate the Casimir interaction energy between a plane suspended graphene sample and a parallel plane ideal conductor. We employ both the Quantum Field Theory (QFT) approach, and the Lifshitz formula generalizations. The first approach turns out to be the leading order in the coupling constant of the second one. The Casimir interaction for this system appears to be rather weak but experimentally measurable. It exhibits a strong dependence on the mass of the quasi-particles in graphene.

We study the field theoretical model of a scalar field in presence of spacial inhomogeneities in form of one and two finite width mirrors (material slabs). The interaction of the scalar field with the defect is described with position-dependent mass term. Within this model we derive the interaction of two finite width mirrors, establish the correspondence of the model to the Lifshitz formula and construct limiting procedure to obtain finite self-energy of a single mirror without any normalization condition.

The Supernovae data, the small value of the Higgs particle mass, and the matter content of the Universe are explained via joint nonlinear realization of the affine and conformal symmetry groups (in spirit of the effective Chiral Lagrangians). This nonlinear realization is used to classify observable physical processes in the Universe, including its origin from the quantum vacuum. All dimension parameters of the theory (including masses and field condensates) arise via quantum anomalies in the beginning of the Universe as consequences of the vacuum postulate. The obtained results are in agreement with last observational and experimental data. These results testify to a super-analog of the joint nonlinear realization as the super-unification of the GR and SM that can be based on the quaternionic supertwistor construction.