International Journal of Modern Physics A

I argue that LHC may shed light on the nature of neutrino mass through the probe of the seesaw mechanism. The smoking gun signature is lepton number violation through the production of same sign lepton pairs, a collider analogy of the neutrinoless double beta decay. I discuss this in the context of left–right symmetric theories, which led originally to neutrino mass and the seesaw mechanism. A W_R gauge boson with a mass in a few TeV region could easily dominate neutrinoless double beta decay, and its discovery at LHC would have spectacular signatures of parity restoration and lepton number violation. Moreover, LHC can measure the masses of the right-handed neutrinos and the right-handed leptonic mixing matrix, which could in turn be used to predict the rates for neutrinoless double decay and lepton flavor violating violating processes. The LR scale at the LHC energies offers great hope of observing these low energy processes in the present and upcoming experiments.

We review the usual account of the phenomena of spontaneous symmetry breaking, pointing out the common misunderstandings surrounding the issue, in particular within the context of quantum field theory. In fact, the common explanations one finds in this context, indicate that under certain conditions corresponding to the situation called spontaneous symmetry breaking, the vacuum of the theory does not share the symmetries of the Lagrangian. We explain in detail why this statement is incorrect in general, and in what limited set of circumstances such a situation could arise. We concentrate on the case of global symmetries, for which we found no satisfactory exposition in the existing literature, and briefly comment on the case of gauge symmetries where, although insufficiently publicized, accurate and complete descriptions exist. We briefly discuss the implications for the phenomenological manifestations usually attributed to the phenomena of spontaneous symmetry breaking, analyzing which might be affected by our analysis and which are not. In particular we describe the mass generation mechanism in a fully symmetric scheme (i.e. with a totally symmetric vacuum), and briefly discuss the implications of this analysis to the problem of formation of topological defects in the early universe.

We have studied the quantum equivalence in the respective strong coupling limits of the bidimensional gauged Thirring model with both Schwinger and Thirring models. It is achieved following a nonperturbative quantization of the gauged Thirring model into the path-integral approach. First, we have established the constraint structure via the Dirac's formalism for constrained systems and defined the correct vacuum–vacuum transition amplitude by using the Faddeev–Senjanovic method. Next, we have computed exactly the relevant Green's functions and shown the Ward–Takahashi identities. Afterwards, we have established the quantum isomorphisms between gauged Thirring model and both Schwinger and Thirring models by analyzing the respective Green's functions in the strong coupling limits, respectively. A special attention is necessary to establish the quantum isomorphism between the gauged Thirring model and the Thirring model.

The Hamiltonian of two modes coupled harmonic oscillators in noncommutative phase-space can be expressed in the standard quadric form by introducing a coordinate transformation. As a result, the coupling items are eliminated and the Hamiltonian can be simplified to the two modes independent harmonic oscillators. Then, the corresponding energy spectrums are obtained with an algebraic method.

The matter spectrum of the MSSM, including three right-handed neutrino supermultiplets and one pair of Higgs–Higgs conjugate superfields, can be obtained by compactifying the E₈ ×E₈ heterotic string and M-theory on Calabi–Yau manifolds with specific SU(4) vector bundles. These theories have the standard model gauge group augmented by an additional gauged U(1)_B-L. Their minimal content requires that the B-L gauge symmetry be spontaneously broken by a vacuum expectation value of at least one right-handed sneutrino. In previous papers, we presented the results of a quasianalytic renormalization group analysis showing that B-L gauge symmetry is indeed radiatively broken with an appropriate B-L/electroweak hierarchy. In this paper, we extend these results by (1) enlarging the initial parameter space and (2) explicitly calculating the renormalization group equations numerically. The regions of the initial parameter space leading to realistic vacua are presented and the B-L/electroweak hierarchy computed over these regimes. At representative points, the mass spectrum for all sparticles and Higgs fields is calculated and shown to be consistent with present experimental bounds. Some fundamental phenomenological signatures of a nonzero right-handed sneutrino expectation value are discussed, particularly the cosmology and proton lifetime arising from induced lepton and baryon number violating interactions.

In the framework of the topcolor-assisted technicolor (TC2) model, we study the neutral top-Higgs production processes , and . The results show that the production rates can reach the level of a few fb with reasonable parameter values. With the clean background of the flavor-changing channel, the top-Higgs events can possibly be detected at the International Linear Collider (ILC) experiments. Therefore, such neutral top-Higgs production processes offer a useful way to probe for neutral top-Higgs and test the TC2 model directly.

In this paper, we study the idea about gravity as entropic force proposed by Verlinde. By interpreting Euclidean gravity in the language of thermodynamic quantities on holographic screen, we find the gravitational force can be calculated from the change of entropy on the screen. We show that normal gravity calculation can be reinterpreted in the language of thermodynamic variables. We also study the fluctuation of the force and find the fluctuation acting on the point-like particle can never be larger than the expectation value of the force. For a black hole in AdS space, by gauge/gravity duality, the fluctuation may be interpreted as arising from thermal fluctuation in the boundary description. And for a black hole in flat space, the ratio between fluctuation and force goes to a constant at infinity.

Field equations in the presence of cosmic string source are obtained in Barber's second self-creation theory of gravitation (Gen. Relativ. Gravit.14, 117 (1982)) with the aid of Einstein–Rosen cylindrically symmetric metric. A static vacuum model and a nonstatic exact string cosmological model are presented which represents Reddy string (Astrophys. Space Sci.286, 365 (2003)) in self-creation theory. Some physical and kinematical properties of the model are also discussed.