Spin-orbit hybrid entanglement quantum key distribution scheme

We propose a novel quantum key distribution scheme by using the SAM-OAM hybrid entangled state as the physical resource.To obtain this state,the polarization entangled photon pairs are created by the spontaneous parametric down conversion process,and then,the q-plate acts as a SAM-to-OAM transverter to transform the polarization entangled pairs into the hybrid entangled pattern,which opens the possibility to exploit the features of the higher-dimensional space of OAM state to encode information.In the manipulation and encoding process,Alice performs the SAM measurement by modulating the polarization stateπ lθx on one photon,whereas Bob modulates the OAM sector state lx' on the other photon to encode his key elements using the designed holograms which is implemented by the computer-controlled SLM.With coincidence measurement,Alice could extract the key information.It is showed that N-based keys can be encoded with each pair of entangled photon,and this scheme is robust against Eve’s individual attack.Also,the MUBs are not used.Alice and Bob do not need the classical communication for the key recovery.     

Plaquette expansion study of compact U(1) lattice gauge theory in (2 + 1) dimensions

The plaquette expansion is applied to compact U(1) lattice gauge theory in (2 + 1) dimensions to high order: 1/N ⁸ for the ground state energy density and 1/N ⁷ for the anti-symmetric or photon mass gap, where N is defined as the number of plaquettes. Evidence of scaling in the photon mass gap is observed for low order (≤ 1/N ⁴) for inverse coupling values β = 0. 7 to 1. 25 with scaling behaviour given by the weak-coupling formula: M ²/β = exp(-5. 01β + 5. 82) in good agreement with other studies. Higher order results appear to diverge from the scaling slope past the transition point portenting the prospect that the strong coupling trial state in this region gives vise to an asymtotic series in 1/N for the photon mass gap.     

Low-energy impact of a heavy Higgs boson sector

The effective theory which characterizes the low-energy sensitivity of the minimal Weinberg-Salam model to a heavy Higgs boson sector is shown to be the gauged SU(2)_L × U(1) non-linear θ model. This theory is the limit of the Weinberg-Salam model as the Higgs boson mass, M_H, is removed (M_H → ∞). Using the symmetry properties of the non-linear theory, along with a power-counting analysis, we are able to classify low-energy observables according to their sensitivity to the regulator (M_H). At one loop, the greatest sensitivity is a logarithmic dependence on the Higgs boson mass. The M_H dependent corrections to some specific, experimentally accessible observables are calculated, and other possible applications of this technique are discussed.     

Two-loop quantum corrections to the soliton mass in two-dimensional scalar field theories

We study higher-order corrections to the soliton mass in two-dimensional scalar field theories.We show that the second quantum correction (two-loop graphs) to the soliton mass (M_S) is finite provided one orders correctly the non-commuting operators in the effective hamiltonian. That is, the vacuum sector UV counterterm suffices to eliminate the ultraviolet and infinite volume divergences of the one-soliton sector.We evaluate explicitly the finite part of the second quantum correction to M_S in the sine-Gordon model. We find that the ratio of the soliton mass to the meson mass is the same in our perturbative calculation, as in the semiclassical one by Dashen, Hasslacher and Neveu, up to two-loop contributions.     

String quantization in accelerated frames and black holes

We quantize a closed bosonic string in a light-cone gauge in Rindler (uniformly accelerated) space-time and apply it to the Schwarzschild-Kruskal manifold. Inertial and accelerated particle states of the string associated to positive frequency modes with respect to the inertial and Rindler times respectively, are defined. There is a stretching effect of the string due to the presence of an event horizon. We explicitly solve the dynamical constraints leaving as physical degrees of freedom only those transverse to the acceleration. Different mass formulae are introduced depending on whether the centre of mass of the string has uniform speed or uniform acceleration. The expectation value of the Rindler (Schwarzschild) number-mode operator in the string around state (tachyon) results equal to a thermal spectrum at the Hawking-Unruh temperature T_s=α/2π (∼ M_Pl(M_Pl/M)^1/(D−3), where M is the black hole mass). We find T₀=M′/2π where M′ is the accelerated ground state string mass and T₀ the temperature T_s in dimensionless frequency units. Correlation functions of string coordinates and vertex operators and their Fourier transforms in accelerated time (string response functions) are computed and their thermal properties analyzed.     

Weak-coupling expansion of the low-lying energy values in the SU(2) gauge theory on a torus

Relying on analytic results obtained previously, we complete the one-loop computation of the low-lying energy values of the SU(2) gauge theory in an L × L × L periodic box. The expansions are then rewritten in terms of the universal parameter z = M(0⁺) · L (M(0⁺): energy gap in the J^p = 0⁺ sector). We find that the crossover from small-volume to large-volume behaviour is likely to take place at z ? 2. Furthermore, near the crossover, the lowest energy levels (above the ground state) in the 0⁺ sector and the 2⁺ sector are practically degenerate. In each of these sectors there is one more state at about 1.5 · M(0⁺). In the 0^? sector, on the other hand, the lowest energy value is greater than 3 · M(0⁺).     

Stimulated two-photon emission from excitonic molecules in ZnO

The M-band emission in ZnO at 1.7 K is investigated by tuning the excitation light through the A-B exciton region. Externally stimulated two-photon emission from excitonic molecules is observed when the pump photon energy is resonant with the upper B-polariton. The experiments suggest two excitonic molecule levels separated by 4.6 meV and with a ground state energy E_M = 6.7394 eV.     

Decay of Z boson into photon and unparticle

We study the decay of the standard model Z boson into unparticle plus a single photon through a one-loop process. As in the anomaly type decay, only the axial-vector part of the Z coupling matching with the vector unparticle and/or the vector part of the Z coupling matching with the axial-vector unparticle can give a nonzero contribution to the decay. We show that the photon spectrum terminates at the end point in accord with Yang's theorem. Existing data on single photon production at LEP I is used to constrain the unparticle sector.     

SU(7) Electroweak unification

Electroweak unification is obtained in anSU(7) model at a mass scale 3×10¹⁰≦M≦3×10¹⁶ GeV's, with left-right symmetric subgroups and sin² θ _w (M)=3/8. BelowM, the model reduces toSU(3) _L ×SU(3) _R , the flavor sector of the “trinification theory” of Glashow et al., or of theE ₆ grand unified theory. This model predicts a natural massless neutrino, and fractionally charged leptons with masses in theM regime.     

Lorentz violation at high energy: Concepts, phenomena, and astrophysical constraints

We consider here the possibility of quantum gravity induced violation of Lorentz symmetry (LV). Even if suppressed by the inverse Planck mass such LV can be tested by current experiments and astrophysical observations. We review the effective field theory approach to describing LV, the issue of naturalness, and many phenomena characteristic of LV. We discuss some of the current observational bounds on LV, focusing mostly on those from high energy astrophysics in the QED sector at order E/M_Planck. In this context, we present a number of new results which include the explicit computation of rates of the most relevant LV processes, the derivation of a new photon decay constraint, and modification of previous constraints taking proper account of the helicity dependence of the LV parameters implied by effective field theory.     

On the motion of a particle with anisotropic mass

On the basis of the hypothesis that particle mass is anisotropic rather than isotropic, we investigate the relativistic motion of a particle within the framework of flat space-time. Assuming that the mass anisotropy is associated with the photon cloud of the particle, we argue that the self-energy of a particle is of the order of magnitude |δ m/M ₀|?0.0005, for which conventional quantum electrodynamics, however, gives an infinite value.     

W-Boson mass operator in an external magnetic field at high temperatures

By the Schwinger proper-time method, the one-loop contribution to the W-boson mass operator is calculated in a constant magnetic field at high temperatures. The static limit is investigated. By averaging the mass operator over the physical states of a vector particle, the temperature-dependent radiative corrections to the W-boson energy spectrum are obtained at high magnetic fields (eH/M ²?1) for various values of the spin projection onto the field direction. These corrections are found to be positive. In particular, the correction to the ground-state level stabilizes the W-boson vacuum state at high temperatures.     

Equivalence of Two Definitions of the Effective Mass of a Polaron

Two definitions of the effective mass of a particle interacting with a quantum field, such as a polaron, are considered and shown to be equal in models similar to the Fröhlich polaron model. These are: 1. the mass defined by the low momentum energy E(P)≈E(0)+P ²/2M of the translation invariant system constrained to have momentum P and 2. the mass M of a simple particle in an arbitrary slowly varying external potential, V, described by the nonrelativistic Schrödinger equation, whose ground state energy equals that of the combined particle/field system in a bound state in the same V.     

A unified approach to resonances and partons: A survey of the problems and accomplishments

A brief survey of the recently proposed unified approach to resonances and partons is presented. A new result is the formula for the mean value of the mass of the parton, $\text{m}\text{= (1 ? ad)M}{}_{\mathrm{n}}$, where a is the average distance between the adjacent hadronic levels, d the radius of the nucleon, and M_n its mass. We also discuss the spacelike states in more detail and give a possible parton model interpretation of this less familiar physical phenomenon.     

X-ray M4,5 resonant Raman scattering from Gd with final 4p hole: calculations with 4p–4d–4f configuration interaction in the final state and comparison with the experiment

We present calculations of resonant Raman scattering (RRS) at the M_4,5 thresholds of Gd in the scattering channel 3d¹⁰4f⁷→3d⁹4f⁸→[4p⁵4f⁸↔4d⁸4f⁹]. We have included in the final state the interaction between the two configurations within the brackets, having one 4p and two 4d holes, respectively. The influence of the configuration interaction on the scattering spectra is shown to be important. The calculations are made within a purely ionic model including only the spectral features dispersing with the incident photon energy and do not account for the M₄ to M₅ Coster-Kronig conversion. The calculations are compared with recent experimental results on Gd metal. The agreement is excellent when choosing the excitation energy in the M₅ region. In the M₄ region the calculations agree with the measurements by assuming that the Coster-Kronig contribution is approximated in shape by the RRS spectrum measured with direct M₅ excitation. The implications of the results are discussed.     

Weak interaction effects in positronium

Within the context of the Weinberg-Salam (standard) model we study possible effects of weak interactions in positronium (Ps), such as parity mixing and weak decays of Ps states. As expected, weak interaction amplitudes in Ps turn out to be extremely small, their magnitude being characterized byG·m _e ² ?3·10^?12 whereG is Fermi's constant andm _e the electron mass. We show that the standard model forbids parity-violating correlations in a large class of Ps reactions and decays due to CP conservation in the lepton sector. We then consider situations in which parity-odd effects in Ps will occur in the standard model and may even be large enough to be observable. Beyond the context of the standard model we discuss the decay of orthopositronium into a photon and the hypothetical axion under the assumption that the mass of the axion is smaller than twice the mass of the electron.     

How to testCP,T, andCPT invariance in the three photon decay of polarized3 S 1 positronium

We investigate whether and how the three photon decay of polarizedj=1 positronium (Ps), in particular³ S ₁ Ps, can be used for tests ofCP, T, andCPT invariance. A general analysis is made in terms of thePs decay matrix. We consider some angular correlations sensitive to possibleCP violation and calculate their expectation values assuming thatCP violation occurs in thePs mass matrix only. Furthermore we discuss some models ofCP violation in the lepton sector and their implications forCP violation inPs mixing and decay. Finally we calculate the contributions due to photon-photon final state interactions to some correlations which are naively, i.e. in the Coulomb approximation,T-andCPT-odd.     

Physical null zones and radiation representation

General conditions for reconstructing physical null radiation zones in single photon tree amplitudes are given. The systematic analysis has been carried out using invariant quantities. For arbitrary values of masses and charges these zones are always smaller than in the massless and equal charges case. As an application the radiative W boson decay into heavy quarks is studied. This process turns out be a rather sensitive test of the current quark masses m_q(M_W²), as well as of the $\text{q}$qW, q$\text{q}$γ and W⁺W^?γ vertices. This is to the presence of a null line in the photon phase space with a location which strongly depends on m_q. A recently proposed radiation representation for single photon tree amplitudes is analyzed. Explicit examples are given for a number of cases including fermion and vector boson lines.     

Nonlinear σ-model and nucleon structure

The nonlinear σ-model with the Wess-Zumino action describes the nucleon as a soliton and incorporates the non-abelian chiral anomalies. Several studies have shown that the model works well except for the nucleon mass, which comes out consistently too large. We investigate this question beginning with the more general framework of the linear σ-model, which has besides a pseudoscalar meson sector, a fermion or quark sector, a scalar field and an interaction between the fermions via the scalar field. Using a path integral formulation, we express the fermion measure of the model as the product of a Jacobian and an invariant measure. Identifying this Jacobian as exp[iΓ _wz] , we find that the model breaks up into two parts, when in the pseudoscalar meson sector the scalar field is replaced by its vacuum value. The pseudoscalar part of the model becomes the nonlinear σ-model with the Wess-Zumino actionΓ _wz. The other part involves chiral fermions, the scalar field and their interaction. We continue this part back to the Minkowski space to determine its ground state and energy levels. We find that for a scalar field that vanishes at smallr, but rises sharply to its vacuum value at someR, the ground state energy of the interacting quark-scalar-field system can be lower than the ground state energy of the non-interacting quark system. This means the interaction between quarks and the scalar field can lead to a condensed ground state or vacuum and can reduce the overall energy of the system (a phase transition as in superconductivity). It is, therfore, not surprising that the nonlinear σ-model predicts too large a nucleon mass, since it implicitly assumes a normal non-interacting vacuum in the quark sector. Quarks are now quasiparticles that appear as excitations of the condensed vacuum. The nucleon structure that emerges from this investigation agrees fully with the phenomenological nucleon structure found from analysis of high energy elasticpp and \(\bar p\) p scattering at CERN ISR and SPS Collider.     

Microscopic theory of brownian motion: III. The nonlinear Fokker-Planck equation

The nonlinear Fokker-Planck equation for the momentum distribution of a brownian particle of mass M in a bath of particles of mass m is derived. The contribution to this equation arising from initial deviation from bath equilibrium is analysed. This contribution is free of slow M-dependent decays and with certain restrictions leads to an effective shift in the initial value of the B particle momentum. The nonlinear Fokker-Planck equation for an initial bath equilibrium state is analyzed in terms of its predictions for momentum relaxation and mode coupling effects. It is found that in addition to nonlinear renormalization of the type previously found for the momentum correlation function, mode coupling leads to long-lived memory of the initial momentum state.