Status Report on Universal Extra Dimensions After LHC8

Although they do not address the hierarchy problem, models with Universal Extra Dimensions have attracted a lot of attention as simple benchmark models characterized by small mass splittings and a dark matter WIMP played by the Lightest Kaluza-Klein particle (LKP). We review their status, with emphasis on the minimal implementation in 5 dimensions (MUED) in which the LKP is a massive hypercharge gauge boson. In this case, the mass range accounting for the correct dark matter abundance (around 1.4 TeV) remains untouched by LHC8 and is out of reach of present DM direct detection experiments. However, LHC14 can probe the relevant region in the 3-lepton channel.Comment: Invited review for special issue on "Extra dimensions vs Collider Physics" to appear in IJMPA. 14 pages, 9 figures; v2: Figure 5 clarified and references added; v3:comment added on low cutoff cas

Higgsogenesis

In addition to explaining the masses of elementary particles, the Higgs boson may have far-reaching implications for the generation of the matter content in the Universe. For instance, the Higgs plays a key role in two main theories of baryogenesis, namely electroweak baryogenesis and leptogenesis. In this letter, we propose a new cosmological scenario where the Higgs chemical potential mediates asymmetries between visible and dark matter sectors, either generating a baryon asymmetry from a dark matter asymmetry or vice-versa. We illustrate this mechanism with a simple model with two new fermions coupled to the Higgs and discuss associated signatures.Comment: 5 pages, 2 figures; v2: Intro and conclusion improved, clarifications added, results unchanged. Compared to the PRL version, this arxiv version contains two extra plots, one additional table and a slightly longer conclusio

Gravitational Waves from Phase Transitions at the Electroweak Scale and Beyond

If there was a first order phase transition in the early universe, there should be an associated stochastic background of gravitational waves. In this paper, we point out that the characteristic frequency of the spectrum due to phase transitions which took place in the temperature range 100 GeV - 10^7 GeV is precisely in the window that will be probed by the second generation of space-based interferometers such as the Big Bang Observer (BBO). Taking into account the astrophysical foreground, we determine the type of phase transitions which could be detected either at LISA, LIGO or BBO, in terms of the amount of supercooling and the duration of the phase transition that are needed. Those two quantities can be calculated for any given effective scalar potential describing the phase transition. In particular, the new models of electroweak symmetry breaking which have been proposed in the last few years typically have a different Higgs potential from the Standard Model. They could lead to a gravitational wave signature in the milli-Hertz frequency, which is precisely the peak sensitivity of LISA. We also show that the signal coming from phase transitions taking place at T ~ 1-100 TeV could entirely screen the relic gravitational wave signal expected from standard inflationary models.Comment: 18 pages, 24 figure

Extra Dimensions at the LHC

We discuss the motivation and the phenomenology of models with either flat or warped extra dimensions. We describe the typical mass spectrum and discovery signatures of such models at the LHC. We also review several proposed methods for discriminating the usual low-energy supersymmetry from a model with flat (universal) extra dimensions. (For the official website of the book, see http://cambridge.org/us/catalogue/catalogue.asp?isbn=9780521763684 .)Comment: 33 pages, 17 figure

Payment periods in 2009 - one year on from the economic modernisation act.

Payemnt periods shortened in 2009. The decline is no longer due entirely to SMEs; it now concerns MTEs a well as large companies. It generates cash earnings, chiefly for SMEs.activity, profitability, debt, investment, SMEs, MTEs.

Indirect Detection of Kaluza-Klein Dark Matter

We investigate prospects for indirect detection of Kaluza--Klein dark matter, focusing on the annihilation radiation of the first Kaluza--Klein excitation of the Hypercharge gauge boson $B^{(1)}$ in the Galactic halo, in particular we estimate neutrino, gamma-ray and synchrotron fluxes. Comparing the predicted fluxes with observational data we are able to constrain the $B^{(1)}$ mass (and therefore the compactification scale). The constraints depend on the specific model adopted for the dark matter density profile. For a NFW profile the analysis of synchrotron radiation puts a lower bound on the $B^{(1)}$ mass of the order of $\simeq 300$ GeV.Comment: 8 pages, 9 figures, version accepted for publication in PR

Supergravity Inspired Warped Compactifications and Effective Cosmological Constants

We propose a supergravity inspired derivation of a Randall-Sundrum's type action as an effective description of the dynamics of a brane coupled to the bulk through gravity only. The cosmological constants in the bulk and on the brane appear at the classical level when solving the equations of motion describing the bosonic sector of supergravities in ten and eleven dimensions coupled to the brane. They are related to physical quantities like the brane electric charge and thus inherit some of their physical properties. The most appealing property is their quantization: in d_\perp extra dimensions, Lambda_brane goes like N and Lambda_bulk like N^{2/(2-d_perp)}. This dynamical origin also explains the apparent fine-tuning required in the Randall-Sundrum scenario. In our approach, the cosmological constants are derived parameters and cannot be chosen arbitrarily; instead they are determined by the underlying Lagrangian. Some of the branes we construct that support cosmological constant in the bulk have supersymmetric properties: D3-branes of type IIB superstring theory provide an explicit example.Comment: 17 pages, LaTeX, 1 figure. v2: references added and a comment about D-8 brane of massive IIA sugra included v3: improved argument on the effective cosmological constants quantization and clarified discussion on the supersymmetric issue of the solutions constructed. Final version to appear in NP