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Rainer Dick

Publications and source records attributed to Rainer Dick.

At least 37 records · Page 2Linked to original sources
arXiv2012

Coupling of fermionic fields with mass dimensions one to the O'Raifeartaigh model

The objective of this article is to discuss the coupling of fermionic fields with mass dimension one to the O'Raifeartaigh model to study supersymmetry breaking for fermionic fields with mass dimension one. We find that the coupled model has two distinct solutions. The first solution represents a local minimum of the superpotential which spontaneously breaks supersymmetry in perfect analogy to the O'Raifeartaigh model. The second solution is more intriguing as it corresponds to a global minimum of the superpotential. In this case the coupling to the fermionic sector restores supersymmetry. However, this is achieved at the cost of breaking Lorentz invariance. Finally, the mass matrices for the multiplets of the coupled model are presented. It turns out that it contains two bosonic triplets and one fermionic doublet which are mass multiplets. In addition it contains a massless fermionic doublet as well as one fermionic triplet which is not a mass multiplet but rather an interaction multiplet that contains component fields of different mass dimension. These results show that the presented model for fermionic fields with mass dimension one is a viable candidate for supersymmetric dark matter that could be accessible to experiments in the near future.

hep-th↗
arXiv2010

A Supersymmetric Lagrangian for Fermionic Fields with Mass Dimension One

We present the derivation of a supersymmetric model for fermionic fields with integer valued mass dimension based on a general superfield with one free spinor index. First, we demonstrate that it is impossible to formulate such a model based on a general scalar superfield. This is due to problems constructing a Lagrangian containing a kinetic term for the fermionic mass dimension one field, as well as problems deriving a consistent second quantisation. We then develop a formalism based on a general superfield with one free spinor index. We systematically derive all associated chiral and anti-chiral superfields up to third order in covariant derivatives. Using this formalism we are able to construct a supersymmetric on-shell Lagrangian that contains a kinetic term for the fermionic fields with mass dimension one. We then derive the corresponding on-shell supercurrent and succeed to formulate a consistent second quantisation for the component fields. Finally, we present our result for a supersymmetric Hamiltonian. As the Lagrangian is by construction supersymmetric and the Hamiltonian was derived from the Lagrangian using the supersymmetry algebra the Hamiltonian must be positive definite.

hep-th↗
arXiv2009

Supertranslations to all orders

The transformation laws of the general linear superfield and chiral superfields under N=1 supertranslations are tabulated to all orders in the supertranslation parameters.

math-ph↗
arXiv2008

Cosmic rays through the Higgs portal

We consider electroweak singlet dark matter with a mass comparable to the Higgs mass. The singlet is assumed to couple to standard matter through a perturbative coupling to the Higgs particle. The annihilation of a singlet with a mass comparable to the Higgs mass is dominated by proximity to the W, Z and Higgs peaks in the annihilation cross section. We find that the continuous photon spectrum from annihilation of a perturbatively coupled singlet in the galactic halo can reach a level of several per mil of the EGRET diffuse gamma ray flux.

astro-ph↗
arXiv2003

On the Newtonian Limit in Gravity Models with Inverse Powers of R

I reconsider the problem of the Newtonian limit in nonlinear gravity models in the light of recently proposed models with inverse powers of the Ricci scalar. Expansion around a maximally symmetric local background with positive curvature scalar R_0 gives the correct Newtonian limit on length scales << R_0^{-1/2} if the gravitational Lagrangian f(R) satisfies |f(R_0)f''(R_0)|<< 1. I propose two models with f''(R_0)=0.

gr-qc↗
arXiv2001

Ultra-High Energy Cosmic Rays: The Annihilation of Super-Heavy Relics

We investigate the possibility that ultra-high energy cosmic rays (UHECRs) originate from the annihilation of relic superheavy (SH) dark matter in the Galactic halo. In order to fit the data on UHECRs, a cross section of $<σ_Av>\sim 10^{-26}\textrm{cm}^2 (M_X/10^{12} \textrm{GeV})^{3/2}$ is required if the SH dark matter follows a Navarro--Frenk--White (NFW) density profile. This would require extremely large-$l$ contributions to the annihilation cross section. An interesting finding of our calculation is that the annihilation in sub-galactic clumps of dark matter dominates over the annihilations in the smooth dark matter halo, thus implying much smaller values of the cross section needed to explain the observed fluxes of UHECRs.

astro-ph↗
arXiv2001

Ultra-high energy cosmic rays from annihilation of superheavy dark matter

We consider the possibility that ultra-high energy cosmic rays originate from the annihilation of relic superheavy dark-matter particles. We find that a cross section of ~ 10^{-26}cm^2 (M_X/10^{12}GeV)^{3/2} is required to account for the observed rate of super-GZK events if the superheavy dark matter follows a Navarro-Frenk-White density profile. This would require extremely large-l contributions to the annihilation cross section. We also calculate the possible signature from annihilation in sub-galactic clumps of dark matter and find that the signal from sub-clumps dominates and may explain the observed flux with a much smaller cross section than if the superheavy dark matter is smoothly distributed. Finally, we discuss the expected anisotropy in the arrival directions of the cosmic rays, which is a characteristic signature of this scenario.

astro-ph↗
arXiv2001

Standard Cosmology in the DGP Brane Model

Large extra dimensions provide interesting extensions of our parameter space for gravitational theories. There exist now brane models which can perfectly reproduce standard four-dimensional Friedmann cosmology. These models are not motivated by observations, but they can be helpful in developing new approaches to the dimensionality problem in string theory. I describe the embedding of standard Friedmann cosmology in the DGP model, and in particular the realization of our current (dust+Lambda)-dominated universe in this model.

hep-th↗
arXiv2001

Brane worlds

This is an introductory review of gravity on branes with an emphasis on codimension 1 models. However, for a new result it is also pointed out that the cosmological evolution of the 3-brane in the model of Dvali, Gabadadze and Porrati may follow the standard Friedmann equation. Contents: 1. Introduction 2. Conventions 3. The Lanczos-Israel matching conditions 4. The action principle with codimension 1 hypersurfaces: Need for the Gibbons-Hawking term 5. The Newtonian limit on thin branes 6. A remark on black holes in the model of Dvali, Gabadadze and Porrati 7. The cosmology of codimension 1 brane worlds

hep-th↗
arXiv2000

Which action for brane worlds?

In his pioneering work on singular shells in general relativity, Lanczos had derived jump conditions across energy-momentum carrying hypersurfaces from the Einstein equation with codimension 1 sources. However, on the level of the action, the discontinuity of the connection arising from a codimension 1 energy-momentum source requires to take into account two adjacent space-time regions separated by the hypersurface. The purpose of the present note is to draw attention to the fact that Lanczos' jump conditions can be derived from an Einstein action but not from an Einstein-Hilbert action.

hep-th↗
arXiv1998

Convergent Perturbation Theory for a q-deformed Anharmonic Oscillator

A $q$--deformed anharmonic oscillator is defined within the framework of $q$--deformed quantum mechanics. It is shown that the Rayleigh--Schrödinger perturbation series for the bounded spectrum converges to exact eigenstates and eigenvalues, for $q$ close to 1. The radius of convergence becomes zero in the undeformed limit.

math.QA↗
arXiv1998

Confinement from a massive scalar in QCD

A model is introduced with a massive scalar coupling to the Yang--Mills term in four--dimensional gauge theory. It is shown that the resulting potential of colour sources consists of a short range Coulomb interaction and a long range confining part. Far away from the source the scalar vanishes $\sim r^{-1}$ while the potential diverges linearly $\sim r$. Up to an $N_c$--dependent factor of order 1 the tension parameter in the model is $gmf$, where $m$ denotes the mass of the scalar and $f$ is a coupling scale entering the scalar--gluon coupling.

hep-ph↗
arXiv1997

The string scale and the Planck scale

A particle spectrum below the string scale in accordance with predictions from heterotic string theory yields a Planck mass $m_{Pl}=(8πG_N)^{-1/2}$ which exceeds the string scale by a factor $\simeq 61.9$. A Planck mass $m_{Pl}=2.43\times 10^{18}$ GeV then corresponds to a string scale $m_s=3.9\times 10^{16}$ GeV. Such a low value for the string scale in turn implies that the relative strength of graviton and vector exchange in the string/M-theory phase exceeds the corresponding ratio in the low energy field theory.

hep-th↗
arXiv1997

Vector and scalar confinement in gauge theory with a dilaton

In a recent letter it has been shown that gauge theory with a dilaton provides linearly increasing gauge potentials from static or uniformly moving pointlike colour sources. This ensures confinement in the framework of no-pair equations. Here I would like to point out that a dilaton coupling both to the gauge curvature term and to fermion masses yields a linear potential with a scalar component and a dominant vector contribution.

hep-ph↗
arXiv1997

Implications of a dilaton in gauge theory and cosmology

After a review of theoretical motivations to consider theories with direct couplings of scalar fields to Ricci and gauge curvature terms, we consider the dynamics and non-perturbative stabilization of a dilaton in three and in four dimensions. In particular, we derive generalized Coulomb potentials in the presence of a dilaton and discuss a low energy effective dilaton potential induced by instanton effects and the S--dual coupling to axions. We conclude with a discussion of cosmological implications of a light dilaton.

hep-th↗
arXiv1997

The Coulomb potential in gauge theory with a dilaton

I calculate the potential of a pointlike particle carrying SU$(N_c)$ charge in a gauge theory with a dilaton. The solution depends on boundary conditions imposed on the dilaton: For a dilaton that vanishes at infinity the resulting potential is of the form $(r+r_ϕ)^{-1}$, with $r_ϕ$ inverse proportional to the decay constant of the dilaton. Another natural constraint for the dilaton $ϕ$ is independence of $\frac{1}{g^2}\exp(\fracϕ{f_ϕ})$ from the gauge coupling $g$. This requirement yields a potential proportional to $r$ and makes it impossible to create an isolated SU$(N_c)$ charge.

hep-th↗
arXiv1996

The dilaton as a candidate for dark matter

We examine consequences of the stabilization of the dilaton through the axion. An estimate of the resulting dilaton potential yields a relation between the axion parameter $m_a f_{PQ}$ and the average instanton radius, and predicts the ratio between the dilaton mass $m_ϕ$ and the axion mass $m_a$. If we identify the string axion with a Peccei--Quinn axion, then $m_ϕm_{Pl} \sim m_a f_{PQ}$, and the dilaton should be strongly aligned $\sqrt{<ϕ^2>}\leq 10^{-4}m_{Pl}$ at the QCD scale, in order not to overclose the universe.

hep-th↗