Photon Propagation as a Probe for Fundamental Physics

In this thesis we show how light propagation can be used in order to constrain particle physics models beyond the Standard Model. We study in particular the effects of non standard physics on the polarization of cosmic microwave background radiation and on the flux of ultrahigh energy γ-rays (Eγ > 1019 eV). In the first part we discuss the effects on cosmic microwave background polarization of coupling between photons and pseudoscalar fields acting as dark matter (e.g. axions) or as dark energy (e.g. ultralight pseudo Nambu- Goldstone bosons). In particular we describe how the public code CAMB can be modified in order to take into account the rotation of the linear polarization plane from last scattering surface to nowadays, produced by photon propagation in a cosmological background of pseudoscalar particles. Polarization power spectra are compared with the ones obtained in the widely used approximation in which the rotation angle is assumed constant in time. We show how polarization-polarization and temperature-polarization angular power spectra can be very useful to constrain the coupling constant gφ between photons and pseudoscalars. In the second part of this thesis we use the current upper limits on the flux of ultrahigh-energy photons in order to constrain Lorentz invariance violating terms in the dispersion relations for elementary particles. Theories trying to unify quantum mechanics with general relativity and many supersymmetry models predict indeed that Lorentz symmetry has to be modified at energies of the order of the Planck scale (1028 eV). If standard dispersion relations of elementary particles are modified, then the propagation and therefore also the energy spectrum of ultrahigh-energy cosmic rays can be considerably changed. We study in particular how it is possible to constrain Lorentz invariance violating terms for photons and electrons (suppressed both at first and second order of the Planck mass) improving current constraints by several orders of magnitude. The main results are summarized in the following papers: • F. Finelli and M. Galaverni, “Rotation of Linear Polarization Plane and Circular Polarization from Cosmological Pseudoscalar Fields,” arXiv:0802.4210 [astro-ph], submitted. • M. Galaverni, F. Finelli, “Systematics of Cosmic Microwave Background Polarization,” Internal Report IASF-BO 454/2007. • M. Galaverni and G. Sigl, “Lorentz Violation in the Photon Sector and Ultra-High Energy Cosmic Rays,” Phys. Rev. Lett. 100, 021102 (2008) [arXiv:0708.1737 [astro-ph]]. • M. Galaverni and G. Sigl, “Lorentz Violation and Ultrahigh-Energy Photons,” Phys. Rev. D 78, 063003 (2008) [arXiv:0807.1210 [astroph]]

Lorentz Violation for Photons and Ultra-High Energy Cosmic Rays

Lorentz symmetry breaking at very high energies may lead to photon dispersion relations of the form omega^2=k^2+xi_n k^2(k/M_Pl)^n with new terms suppressed by a power n of the Planck mass M_Pl. We show that first and second order terms of size xi_1 > 10^(-14) and xi_2 < -10^(-6), respectively, would lead to a photon component in cosmic rays above 10^(19) eV that should already have been detected, if corresponding terms for electrons and positrons are significantly smaller. This suggests that Lorentz invariance breakings suppressed up to second order in the Planck scale are unlikely to be phenomenologically viable for photons.Comment: 4 revtex pages, 3 postscript figures included, version published in PR

Jordan and Einstein Frames from the perspective of ω=−3/2\omega=-3/2 Hamiltonian Brans-Dicke theory

We carefully perform a Hamiltonian Dirac's constraint analysis of $\omega=-\frac{3}{2}$ Brans-Dicke theory with Gibbons-Hawking-York (GHY) boundary term. The Poisson brackets are computed via functional derivatives. After a brief summary of the results for $\omega\neq-\frac{3}{2}$ case, we derive all Hamiltonian Dirac's constraints and constraint algebra both in the Jordan and Einstein frames. Confronting and contrasting Dirac's constraint algebra in both frames, it is shown that they are not equivalent. This highlights the transformations from the Jordan to the Einstein frames are not Hamiltonian canonical transformations.Comment: corrected some typos, more references adde

Search for photons at the Pierre Auger Observatory

The Pierre Auger Observatory has a unique potential to search for ultra-high energy photons (above ~1 EeV). First experimental limits on photons were obtained during construction of the southern part of the Observatory. Remarkably, already these limits have proven useful to falsify proposals about the origin of cosmic rays, and to perform fundamental physics by constraining Lorentz violation. A final discovery of photons at the upper end of the electromagnetic spectrum is likely to impact various branches of physics and astronomy.Comment: 5 pages, 5 figures. Presented at CRIS 2008, Malfa, Ital

Per un uso non ordinario della vita e della poesia : su Wisława Szymborska

This article is of a comparative nature and attempts to contrast the poetic output of two Nobel prize-winners, i.e. Eugenio Montale and Wisława Szymborska. The author uncovers numerous similarities especially between Montale’s late works and Szymborska’s poetry. This is particularly visible on two planes, i.e. existential reflection and language, as well as poetic means. The Italian poet and Polish poetess focus on the individual presented as being under pressure from the modern world’s vast, impersonal forces, e.g. history, progress etc. They treat the traditional poetic means of expression with mistrust and instead favour the kind of language that is as clear as possible, subject to philosophical reflection, and infused with irony, allegory and paradox

Cosmological birefringence constraints from CMB and astrophysical polarization data

Cosmological birefringence is a rotation of the polarization plane of photons coming from sources of astrophysical and cosmological origin. The rotation can also depend on the energy of the photons and not only on the distance of the source and on the cosmological evolution of the underlying theoretical model. In this work, we constrain few selected models for cosmological birefringence, combining CMB and astrophysical data at radio, optical, X and gamma wavelengths, taking into account the specific energy and distance dependences.Comment: 12 pages, 2 figure

Ecological genetics and conservation genomics of wolf (Canis lupus)

In the present work, we apply both traditional and Next Generation Sequencing (NGS) tools to investigate some of the most important adaptive traits of wolves (Canis lupus). In the first part, we analyze the variability of three Major Histocompatibility Complex (MHC) class II genes in the Italian wolf population, also studying their possible role in mating choice and their influence on fitness traits. In the second section, as part of a larger canid genome project, we will exploit NGS data to investigate the transcript-level differences between the wolf and the dog genome that can be correlated to domestication

Limits on Cosmological Birefringence from the Ultraviolet Polarization of Distant Radio Galaxies

We report on an update of the test on the rotation of the plane of linear polarization for light traveling over cosmological distances, using a comparison between the measured direction of the UV polarization in 8 radio galaxies at z>2 and the direction predicted by the model of scattering of anisotropic nuclear radiation, which explains the polarization. No rotation is detected within a few degrees for each galaxy and, if the rotation does not depend on direction, then the all-sky-average rotation is constrained to be \theta = -0.8 +/- 2.2. We discuss the relevance of this result for constraining cosmological birefringence, when this is caused by the interaction with a cosmological pseudo-scalar field or by the presence of a Cherns-Simons term.Comment: Accepted for publication in The Astrophysical Journal: changed to correspond to the proof-read versio

Wolf outside, dog inside? The genomic make-up of the Czechoslovakian Wolfdog

Background Genomic methods can provide extraordinary tools to explore the genetic background of wild species and domestic breeds, optimize breeding practices, monitor and limit the spread of recessive diseases, and discourage illegal crossings. In this study we analysed a panel of 170k Single Nucleotide Polymorphisms with a combination of multivariate, Bayesian and outlier gene approaches to examine the genome-wide diversity and inbreeding levels in a recent wolf x dog cross-breed, the Czechoslovakian Wolfdog, which is becoming increasingly popular across Europe. Results Pairwise FST values, multivariate and assignment procedures indicated that the Czechoslovakian Wolfdog was significantly differentiated from all the other analysed breeds and also well-distinguished from both parental populations (Carpathian wolves and German Shepherds). Coherently with the low number of founders involved in the breed selection, the individual inbreeding levels calculated from homozygosity regions were relatively high and comparable with those derived from the pedigree data. In contrast, the coefficient of relatedness between individuals estimated from the pedigrees often underestimated the identity-by-descent scores determined using genetic profiles. The timing of the admixture and the effective population size trends estimated from the LD patterns reflected the documented history of the breed. Ancestry reconstruction methods identified more than 300 genes with excess of wolf ancestry compared to random expectations, mainly related to key morphological features, and more than 2000 genes with excess of dog ancestry, playing important roles in lipid metabolism, in the regulation of circadian rhythms, in learning and memory processes, and in sociability, such as the COMT gene, which has been described as a candidate gene for the latter trait in dogs. Conclusions In this study we successfully applied genome-wide procedures to reconstruct the history of the Czechoslovakian Wolfdog, assess individual wolf ancestry proportions and, thanks to the availability of a well-annotated reference genome, identify possible candidate genes for wolf-like and dog-like phenotypic traits typical of this breed, including commonly inherited disorders. Moreover, through the identification of ancestry-informative markers, these genomic approaches could provide tools for forensic applications to unmask illegal crossings with wolves and uncontrolled trades of recent and undeclared wolfdog hybrids

SOX2 Is a Univocal Marker for Human Oral Mucosa Epithelium Useful in Post-COMET Patient Characterization

Total bilateral Limbal Stem Cells Deficiency is a pathologic condition of the ocular surface due to loss or impairment of corneal stem cell function, altering homeostasis of the corneal epithelium. Cultivated Oral Mucosa Epithelial Transplantation (COMET) is the only autologous treatment for this pathology. During the follow-up, a proper characterization of the transplanted oral mucosa on the ocular surface supports understanding the regenerative process. The previously proposed markers for oral mucosa identification (e.g., keratins 3 and 13) are co-expressed by corneal and conjunctival epithelia. Here, we propose a new specific marker to distinguish human oral mucosa from the epithelia of the ocular surface. We compared the transcriptome of holoclones (stem cells) from the human oral mucosa, limbal and conjunctival cultures by microarray assay. High expression of SOX2 identified the oral mucosa vs. cornea and conjunctiva, while PAX6 was highly expressed in corneal and conjunctival epithelia. The transcripts were validated by qPCR, and immunological methods identified the related proteins. Finally, the proposed markers were used to analyze a 10-year follow-up aniridic patient treated by COMET. These findings will support the follow-up analysis of COMET treated patients and help to shed light on the mechanism of corneal repair and regeneration