Scalar modifications to gravity from unparticle effects may be testable

Interest has focussed recently on low energy implications of a nontrivial scale invariant sector of an effective field theory with an IR fixed point, manifest in terms of ``unparticles'' with peculiar properties. If unparticle stuff exists it could couple to the stress tensor and mediate a new 'fifth' force which we call 'ungravity' arising from the exchange of unparticles between massive particles, which in turn could modify the inverse square law. Under the assumption of strict conformal invariance in the hidden sector down to low energies, we compute the lowest order ungravity correction to the Newtonian gravitational potential and find scale invariant power law corrections of type $(R_{G}/r)^{2d_{\cal U} -1}$ where $d_{\cal U}$ is an anomalous unparticle dimension and $R_{G}$ is a characteristic length scale where the ungravity interactions become significant. $d_{\cal U}$ is constrained to lie the range $d_{\cal U} > 3 (2)$ for a spin 2 (spin 0) unparticle coupling to the stress tensor (and its trace) and leads to modification of the inverse square law with $r$ dependence in the range between $1/r^{4+2\delta} (\delta>0)$, while extra dimension models with warping modify the force law with corrections beginning with terms O$(1/r^3)$ for small $r$ but exponentially suppressed for large $r$. Thus a discrimination between extra dimension models and ungravity is possible in future improved submillimeter tests of gravity.Comment: 10 pages and 1 figure. Accepted for publication in Physical Review Letters. Title changed in the revised version. Original title "Ungravity and its possible test

Leptogenesis and the Small-Angle MSW Solution

The lepton asymmetry created in the out-of-equilibrium decay of a heavy Majorana neutrino can generate the cosmological baryon asymmetry when processed through fast anomalous electroweak reactions. In this work I examine this process under the following assumptions: (1) maximal nu_mu/nu_tau mixing (2) hierarchical mass spectrum m_3 >> m_2 (3) small-angle MSW solution to the solar neutrino deficit. Working in a basis where the charged lepton and heavy neutrino mass matrices are diagonal, I find the following bounds on the heavy Majorana masses M_i: (a) for a symmetric Dirac neutrino mass matrix (no other constraints), an asymmetry compatible with BBN constraints can be obtained for min(M_2,M_3)> 10^{11} GeV; (b) if {\em any} of the Dirac matrix elements vanishes, successful baryogenesis can be effected for a choice of min(M_2,M_3) as low as a few times 10^{9} GeV. The latter is compatible with reheat requirements for supersymmetric cosmologies with sub-TeV gravitino masses.Comment: 12 pages, LaTeX; version to be published in Physics Letters

Exact Nonperturbative Unitary Amplitudes for 1->N Transitions

I present an extension to arbitrary N of a previously proposed field theoretic model, in which unitary amplitudes for $1->8$ processes were obtained. The Born amplitude in this extension has the behavior $A(1->N)^{tree}\ =\ g^{N-1}\ N!$ expected in a bosonic field theory. Unitarity is violated when $|A(1->N)|>1$, or when $N>\N_crit\simeq e/g.$ Numerical solutions of the coupled Schr\"odinger equations shows that for weak coupling and a large range of N>\ncrit, the exact unitary amplitude is reasonably fit by a factorized expression |A(1->N)| \sim (0.73 /N) \cdot \exp{(-0.025/\g2)}. The very small size of the coefficient 1/\g2 , indicative of a very weak exponential suppression, is not in accord with standard discussions based on saddle point analysis, which give a coefficient $\sim 1.\$ The weak dependence on $N$ could have experimental implications in theories where the exponential suppression is weak (as in this model). Non-perturbative contributions to few-point correlation functions in this theory would arise at order $K\ \simeq\ \left((0.05/\g2)+ 2\ ln{N}\right)/ \ ln{(1/\g2)}$in an expansion in powers of$\g2.$Comment: 11 pages, 3 figures (not included

Probing Late Neutrino Mass Properties with Supernova Neutrinos

Models of late-time neutrino mass generation contain new interactions of the cosmic background neutrinos with supernova relic neutrinos (SRNs) through exchange of the on-shell light boson, leading to significant modification of the differential SRN flux observed at earth. We consider Abelian U(1) model for generating neutrino masses at low scales and we show that there is a large parameter space in this model for which the changes induced in the flux by the exchange of the light bosons might allow one to distinguish between neutrinos being Majorana or Dirac particles, the type of neutrino mass hierarchy (normal or inverted or quasi-degenerate), and could also possibly determine the absolute values of the neutrino masses. Measurements of the presence of these effects would be possible at the next-generation water Cerenkov detectors enriched with Gadolinium, or a large 100 kton liquid argon detector.Comment: 29 pages latex, 15 figures included. Version to be published in Phys. Rev. D., added discussion of signal detection for water Cerenkov and liquid argon detectors, and discussion of non-adiabatic vs adiabatic neutrino evolution, new figures added, references updated. Results unchange