Electroweak Instantons, Axions, and the Cosmological Constant

If there is explicit violation of baryon plus lepton number at some energy scale, then the electroweak theory depends upon a {\theta}-angle. Due to a singular integration over small scale size instantons, this {\theta}-dependence is sensitive to very high momentum scales. Assuming that there is no new physics between the electroweak and Planck scales, for an electroweak axion the energy difference between the vacuum at {\theta} /= 0, and that at {\theta} = 0, is of the correct order of magnitude to be the dark energy observed in the present epoch.Comment: 6 pages, 1 figure; N_h is corrected; minor corrections in the tex

A Recursive Method to Calculate UV-divergent Parts at One-Loop Level in Dimensional Regularization

A method is introduced to calculate the UV-divergent parts at one-loop level in dimensional regularization. The method is based on the recursion, and the basic integrals are just the scaleless integrals after the recursive reduction, which involve no other momentum scales except the loop momentum itself. The method can be easily implemented in any symbolic computer language, and an implementation in Mathematica is ready to use.Comment: 10 pages, 1 figure, typos fixed, to appear in Computer Physics Communication

Short Distance Freedom of Quantum Gravity

Fourth order derivative gravity in 3+1-dimensions is perturbatively renormalizable and is shown to describe a unitary theory of gravitons in a limited coupling parameter space. The running gravitational constant which includes graviton contribution is computed. Generically, gravitational Newton's constant vanishes at short distances in this perturbatively renormalizable and unitary theory.Comment: 8 pages, 2 figures, abstract modified, a paragraph added, new references added, typos corrected, version to appear in Physics Letter

Existence of Dyons in Minimally Gauged Skyrme Model via Constrained Minimization

We prove the existence of electrically and magnetically charged particlelike static solutions, known as dyons, in the minimally gauged Skyrme model developed by Brihaye, Hartmann, and Tchrakian. The solutions are spherically symmetric, depend on two continuous parameters, and carry unit monopole and magnetic charges but continuous Skyrme charge and non-quantized electric charge induced from the 't Hooft electromagnetism. The problem amounts to obtaining a finite-energy critical point of an indefinite action functional, arising from the presence of electricity and the Minkowski spacetime signature. The difficulty with the absence of the Higgs field is overcome by achieving suitable strong convergence and obtaining uniform decay estimates at singular boundary points so that the negative sector of the action functional becomes tractable.Comment: 24 page

The quarkynic phase and the Z_{Nc} symmetry

We investigate the interplay between the Z_{Nc} symmetry and the emergence of the quarkyonic phase, adding the flavor-dependent complex chemical potentials \mu_f=\mu+iT\theta_f with (\theta_f)=(0, \theta, -\theta) to the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model. When \theta=0, the PNJL model with the \mu_f agrees with the standard PNJL model with the real chemical potential \mu. When \theta=2\pi/3, meanwhile, the PNJL model with the \mu_f has the Z_{Nc} symmetry exactly for any real \mu, so that the quarkyonic phase exists at small T and large \mu. Once \theta varies from 2\pi/3, the quarkyonic phase exists only on a line of T=0 and \mu larger than the dynamical quark mass, and the region at small T and large \mu is dominated by the quarkyonic-like phase in which the Polyakov loop is small but finite.Comment: 5 pages, 6 figure

Do we need Feynman diagrams for higher orders perturbation theory?

We compute the two and three loop corrections to the beta function for Yang-Mills theories in the background gauge field method and using the background gauge field as the only source. The calculations are based on the separation of the one loop effective potential into zero and positive modes and are entirely analytical. No two or three loop Feynman diagrams are considered in the process.Comment: version published in Phys. Lett.

1/N Resolution to Inflationary eta-Problem

We observe that the dominant one loop contribution to the graviton propagator in the theory of N (N>>1) light scalar fields \phi_a (with masses smaller than M_{pl}/\sqrt{N}) minimally coupled to Einstein gravity is proportional to N while that of graviton-scalar-scalar interaction vertex is N independent. We use this to argue that the coefficient of the R\phi_a^2 term appearing at one loop level is 1/N suppressed. This observation provides a resolution to the \eta-problem, that the slow-roll parameter \eta receives order one quantum loop corrections for inflationary models built within the framework of scalar fields minimally coupled to Einstein gravity, for models involving large number of fields. As particular examples, we employ this to argue in favor of the absence of \eta-problem in M-flation and N-flation scenarios.Comment: 1+13 pages, 3 figure

Spontaneous Breaking of Conformal Invariance and Trace Anomaly Matching

We argue that when conformal symmetry is spontaneously broken the trace anomalies in the broken and unbroken phases are matched. This puts strong constraints on the various couplings of the dilaton. Using the uniqueness of the effective action for the Goldstone supermultiplet for broken ${\cal N}=1$ superconformal symmetry the dilaton effective action is calculated.Comment: 29 pages, 2 figure

Three Generations in Minimally Extended Standard Models

We present a class of minimally extended standard models with the gauge group $SU(3)_C \times SU(N)_L \times U(1)_X$ where for all $N \geq 3$, anomaly cancelation requires three generations. At low energy, we recover the Standard Model (SM), while at higher energies, there must exist quarks, leptons and gauge bosons with electric charges shifted from their SM values by integer multiples of the electron charge up to $\pm [N/2] e$. Since the value N=5 is the highest $N$ consistent with QCD asymptotic freedom, we elaborate on the 3-5-1 model.Comment: 9 pages, v3: version to appear in PL

Baryogenesis and neutron-antineutron oscillation at TeV

We propose a TeV extension of the standard model to generate the cosmological baryon asymmetry with an observable neutron-antineutron oscillation. The new fields include a singlet fermion, an isotriplet and two isosinglet diquark scalars. There will be no proton decay although the Majorana mass of the singlet fermion as well as the trilinear couplings between one isosinglet diquark and two isotriplet diquarks softly break the baryon number of two units. The isosinglet diquarks couple to two right-handed down-type quarks or to a right-handed up-type quark and a singlet fermion, whereas the isotriplet diquark couples to two left-handed quarks. The isosinglet diquarks mediate the three-body decays of the singlet fermion to realize a TeV baryogenesis without fine tuning the resonant effect. By the exchange of one singlet fermion and two isosinglet diquarks and of one isosinglet diquark and two isotriplet diquarks, a neutron-antineutron oscillation is allowed to verify in the future experiments.Comment: 5 pages, 2 figure