Hidden Photons in Extra Dimensions

Additional U(1) gauge symmetries and corresponding vector bosons, called hidden photons, interacting with the regular photon via kinetic mixing are well motivated in extensions of the Standard Model. Such extensions often exhibit extra spatial dimensions. In this note we investigate the effects of hidden photons living in extra dimensions. In four dimensions such a hidden photon is only detectable if it has a mass or if there exists additional matter charged under it. We note that in extra dimensions suitable masses for hidden photons are automatically present in form of the Kaluza-Klein tower.Comment: 5 pages, 4 figures; Proceedings of the 9th Patras Workshop on Axions, WIMPs and WISPs, Mainz, June 24-28, 201

Hidden photons with Kaluza-Klein towers

One of the simplest extensions of the Standard Model (SM) is an extra U(1) gauge group under which SM matter does not carry any charge. The associated boson -- the hidden photon -- then interacts via kinetic mixing with the ordinary photon. Such hidden photons arise naturally in UV extensions such as string theory, often accompanied by the presence of extra spatial dimensions. In this note we investigate a toy scenario where the hidden photon extends into these extra dimensions. Interaction via kinetic mixing is observable only if the hidden photon is massive. In four dimensions this mass needs to be generated via a Higgs or Stueckelberg mechanism. However, in a situation with compactified extra dimensions there automatically exist massive Kaluza-Klein modes which make the interaction observable. We present phenomenological constraints for our toy model. This example demonstrates that the additional particles arising in a more complete theory can have significant effects on the phenomenology.Comment: 20 pages, 3 figure

Notes from the 3rd Axion Strategy Meeting

In this note we briefly summarize the main future targets and strategies for axion and general low energy particle physics identified in the "3rd axion strategy meeting" held during the AXIONS 2010 workshop. This summary follows a wide discussion with contributions from many of the workshop attendees.Comment: 5 pages, 1 figur

Decay photons from the axionlike particles burst of type II supernovae

We determine limits from SN 1987A on massive axionlike particles with masses in the 10 keV-100 MeV range and purely coupled to two photons. Axionlike particles produced in the core collapse escape from the star and decay into photons that can be observed as a delayed and diffuse burst. We discuss the time and angular distribution of such a signal. Looking into the future, we also estimate the possible improvements caused by better gamma-ray detectors or the explosion of the red supergiant Betelgeuse in a supernova event

Trembling cavities in the canonical approach

We present a canonical formalism facilitating investigations of the dynamical Casimir effect by means of a response theory approach. We consider a massless scalar field confined inside of an arbitaray domain $G(t)$, which undergoes small displacements for a certain period of time. Under rather general conditions a formula for the number of created particles per mode is derived. The pertubative approach reveals the occurance of two generic processes contributing to the particle production: the squeezing of the vacuum by changing the shape and an acceleration effect due to motion af the boundaries. The method is applied to the configuration of moving mirror(s). Some properties as well as the relation to local Green function methods are discussed. PACS-numbers: 12.20; 42.50; 03.70.+k; 42.65.Vh Keywords: Dynamical Casimir effect; Moving mirrors; Cavity quantum field theory; Vibrating boundary

Cell surface engineering of renal cell carcinoma with glycosylphosphatidylinositol-anchored TIMP-1 blocks TGF-beta 1 activation and reduces regulatory ID gene expression

Tissue inhibitor of metalloproteinase 1 (TIMP-1) controls matrix metalloproteinase activity through 1:1 stoichiometric binding. Human TIMP-1 fused to a glycosylphosphatidylinositol (GPI) anchor (TIMP-1-GPI) shifts the activity of TIMP-1 from the extracellular matrix to the cell surface. TIMP-1-GPI treated renal cell carcinoma cells show increased apoptosis and reduced proliferation. Transcriptomic profiling and regulatory pathway mapping were used to identify the potential mechanisms driving these effects. Significant changes in the DNA binding inhibitors, TGF-beta 1/SMAD and BMP pathways resulted from TIMP-1-GPI treatment. These events were linked to reduced TGF-beta 1 signaling mediated by inhibition of proteolytic processing of latent TGF-beta 1 by TIMP-1-GPI

Chiral phase structure of QCD with many flavors

We investigate QCD with a large number of massless flavors with the aid of renormalization group flow equations. We determine the critical number of flavors separating the phases with and without chiral symmetry breaking in SU(Nc) gauge theory with many fermion flavors. Our analysis includes all possible fermionic interaction channels in the pointlike four-fermion limit. Constraints from gauge invariance are resolved explicitly and regulator-scheme dependencies are studied. Our findings confirm the existence of an Nf window where the system is asymptotically free in the ultraviolet, but remains massless and chirally invariant on all scales, approaching a conformal fixed point in the infrared. Our prediction for the critical number of flavors of the zero-temperature chiral phase transition in SU(3) is Nf^{cr}=10.0\pm 0.29(fermion)[+1.55;-0.63](gluon), with the errors arising from approximations in the fermionic and gluonic sectors, respectively.Comment: 7 pages, 3 figures, updated discussion of the uncertainties in the gauge secto

Axion Helioscopes as Solar Thermometers

Axions, if discovered, could serve as a powerful new messenger for studying astrophysical objects. In this study we show how the Sun's spatial and spectral "axion image" can be inverted to infer the radial dependence of solar properties in a model-independent way. In particular, the future helioscope IAXO may allow us to accurately reconstruct the Sun's temperature profile $T(r)$ in the region up to about 80% (40%) of the solar radius for an axion-photon coupling $g_{a\gamma\gamma}$ of $6 \times 10^{-11}$ GeV$^{-1}$ ($10^{-11}$ GeV$^{-1}$). The statistical fluctuations in the photon data lead to a median precision of better than 10% (16%) in this region, and the corresponding median accuracy was better than 4% (7%). While our approach can simultaneously infer the radial profile of the Debye scale $\kappa_\text{s}(r)$, its weaker connection to the axion production rate leads to median accuracy and precision of worse than 30% and 50%, respectively. We discuss possible challenges and improvements for realistic setups, as well as extensions to more general axion models. We also highlight advantages of helioscopes over neutrino detectors.Comment: 14 + 9 pages, 4 figures, code available at https://github.com/sebhoof/SolarAxionFlu

Axions in string theory — slaying the Hydra of dark radiation

It is widely believed that string theory easily allows for a QCD axion in the cosmologically favored mass range. The required small decay constant, f(a) << M-P, can be implemented by using a large compactification volume. This points to the Large Volume Scenario which in turn makes certain cosmological predictions: first, the closed string axion behaves similarly to a field-theoretic axion in the pre-inflationary scenario, i.e. the initial value can be tuned but one is constrained by isocurvature fluctuations. In addition, the volume represents a long-lived modulus that may lead to an early matter-dominated phase. Finally, the decay of the volume modulus to its own axion tends to overproduce dark radiation. In this paper we aim to carefully analyze the cosmology by studying models that not only allow for a QCD axion but also include inflation. Quite generally, limits on isocurvature fluctuations restrict us to relatively low-scale inflation, which in the present stringy context points to Kahler moduli inflation. As a novel feature we find that the lightest (volume) modulus couples strongly to the Higgs. It hence quickly decays to the SM, thus resolving the original dark radiation problem. This decay is much faster than that of the inflaton, implying that reheating is determined by the inflaton decay. The inflaton could potentially reintroduce a dark radiation problem since it decays to lighter moduli and their axions with equal rates. However, due its mixing with the QCD-saxion, the inflaton has also a direct decay rate to the SM, enhanced by the number of SM gauge bosons. This results in an amount of dark radiation that is consistent with present limits but potentially detectable in future measurements