Gödel-type universes and chronology protection in Hořava–Lifshitz gravity
In the attempts toward a quantum gravity theory, general relativity faces a serious difficulty since it is non-renormalizable theory. Hořava–Lifshitz gravity offers a framework to circumvent this difficulty, by sacrificing the local Lorentz invariance at ultra-high energy scales in exchange of power-counting renormalizability. The Lorentz symmetry is expected to be recovered at low and medium energy scales. If gravitation is to be described by a Hořava–Lifshitz gravity theory there are a number of issues that ought to be reexamined in its context, including the question as to whether this gravity incorporates a chronology protection, or particularly if it allows Godel-type solutions with violation of causality. We show that Hořava–Lifshitz gravity only allows hyperbolic Godel-type space-times whose essential parameters m and ω are in the chronology respecting intervals, excluding therefore any noncausal Godel-type space-times in the hyperbolic class. There emerges from our results that the famous noncausal Godel model is not allowed in Hořava–Lifshitz gravity. The question as to whether this quantum gravity theory permits hyperbolic Godel-type solutions in the chronology preserving interval of the essential parameters is also examined. We show that Hořava–Lifshitz gravity not only excludes the noncausal Godel universe, but also rules out any hyperbolic Godel-type solutions for physically well-motivated perfect-fluid matter content.

title: Complete low-energy effective action in N=4 SYM: A Direct N=2 supergraph calculation
abstract: Using the covariant N=2 harmonic supergraph techniques we calculate the one-loop low-energy effective action of N=4 super-Yang–Mills theory in Coulomb branch with gauge group SU(2) spontaneously broken down to U(1). The full dependence of the low-energy effective action on both the hypermultiplet and gauge fields is determined. The direct quantum calculation confirms the correctness of the exact N=4 SYM low-energy effective action derived in hep-th/0111062 on the purely algebraic ground by invoking a hidden N=2 supersymmetry which completes the manifest N=2 one to N=4. Our results provide an exhaustive solution to the problem of finding out the exact completely N=4 supersymmetric low-energy effective action for the theory under consideration.

title: Horava-Lifshitz-like extensions of supersymmetric theories
abstract: Within the superfield approach, we formulate two different extensions of the Wess-Zumino model and super-QED with Horava-Lifshitz-like additive terms, discuss their quantum properties and calculate lower contributions to the effective action. In the case of the gauge theory, the one-loop effective potential turns out to be gauge independent.

title: Free energy of Lorentz-violating QED at high temperature
abstract: In this paper we study the one- and two-loop contribution to the free energy in QED with Lorentz symmetry breaking introduced via constant CPT-even Lorentz-breaking parameters at the high temperature limit. We find the impact of the Lorentz-violating term for the free energy and carry out a numerical estimation for the Lorentz-breaking parameter.

title: Effective potential for a SUSY Lee–Wick model: The Wess–Zumino case
abstract: Using a superfield generalization of the tadpole method, we study the one-loop effective potential for a Wess–Zumino model modified by a higher derivative term, inspired by the Lee–Wick model. The one-loop Kahlerian potential is also obtained by other methods and compared with the effective potential.

title: Lorentz violation and the proper-time method
abstract: In this Letter, we apply the proper-time method to generate the Lorentz-violating Chern–Simons terms in the four-dimensional Yang–Mills and non-linearized gravity theories. It is shown that the coefficient of the induced Chern–Simons term is finite but regularization dependent.

title: Lepton flavor-violating transitions in effective field theory and gluonic operators
abstract: Lepton flavor-violating processes offer interesting possibilities to probe new physics at multi-TeV scale. We discuss those in the framework of effective field theory, emphasizing the role of gluonic operators. Those operators are obtained by integrating out heavy quarks that are kinematically inaccessible at the scale where low-energy experiments take place and make those experiments sensitive to the couplings of lepton flavor-changing neutral currents to heavy quarks. We discuss constraints on the Wilson coefficients of those operators from the muon conversion ${\ensuremath{\mu}}^{\ensuremath{-}}+(A,Z)\ensuremath{\rightarrow}{e}^{\ensuremath{-}}+(A,Z)$ and from lepton flavor-violating tau decays with one or two hadrons in the final state, e.g., $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\ell}{\ensuremath{\eta}}^{(\ensuremath{'})}$ and $\ensuremath{\tau}\ensuremath{\rightarrow}\ensuremath{\ell}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ with $\ensuremath{\ell}=\ensuremath{\mu},e$. To illustrate the results we discuss explicit examples of constraining parameters of leptoquark models.

title: Constraining New Physics from D0-anti-D0 mixing
abstract: I review constraints on possible New Physics interactions from D0-anti-D0 mixing measurements. I consider the most general low energy effective Hamiltonian and include leading order QCD running of effective operators. I discuss constraints from an extensive list of popular New Physics models, each of which could be discovered at the LHC, that can generate these operators. In most of the scenarios, strong constraints that surpass those from other search techniques could be placed on the allowed parameter space using the existent evidence for observation of D-meson mixing.

title: Searching for super-WIMPs in leptonic heavy meson decays
abstract: We study constraints on the models of bosonic super-weakly interacting particle (super-WIMP) dark matter (DM) with DM masses m X ∼ O ( 1 – 100 ) keV from leptonic decays M → l ν ¯ l + X , where M = B ± , D ± , D s ± is a heavy meson state. We focus on two cases where X denotes either a light pseudoscalar (axion-like), or a light vector state that couples to the standard model (SM) through kinetic mixing. We note that for a small DM mass these decays are separately sensitive to DM couplings to quarks, but not its mass.

title: Searching for light dark matter in heavy meson decays
abstract: Beauty and charm e + e ― factories running at resonance thresholds have unique capabilities for studies of the production of light dark matter particles in the decays of B q (D) meson pairs. We provide a comprehensive study of light dark matter production in heavy meson decays with missing energy E in the final state, such as B q (D 0 ) → E and B q (D 0 ) → γE. We argue that such transitions can be studied at the current flavor factories (and future superflavor factories) by tagging the missing-energy decays with B(D 0 ) decays "on the other side.".

title: Lifetime difference in Bs mixing: Standard Model and beyond
abstract: We present a calculation of 1 / m b 2 corrections to the lifetime differences of B s mesons Δ Γ B s in the heavy-quark expansion. We find that they are small to significantly affect Δ Γ B s and present the result for lifetime difference including non-perturbative 1 / m b and 1 / m b 2 corrections. We also analyze the generic Δ B = 1 New Physics contributions to Δ Γ B s and provide several examples.