The Cosmic Ray p+He energy spectrum in the 3-3000 TeV energy range measured by ARGO-YBJ

The ARGO-YBJ experiment is a full coverage air shower detector operated at the Yangbajing International Cosmic Ray Observatory. The detector has been in stable data taking in its full configuration since November 2007 to February 2013. The high altitude and the high segmentation and spacetime resolution offer the possibility to explore the cosmic ray energy spectrum in a very wide range, from a few TeV up to the PeV region. The high segmentation allows a detailed measurement of the lateral distribution, which can be used in order to discriminate showers produced by light and heavy elements. In this work we present the measurement of the cosmic ray light component spectrum in the energy range 3-3000 TeV. The analysis has been carried out by using a two-dimensional unfolding method based on the Bayes' theorem.Comment: Talk given at RICAP14 conferenc

Quantum state majorization at the output of bosonic Gaussian channels

Quantum communication theory explores the implications of quantum mechanics to the tasks of information transmission. Many physical channels can be formally described as quantum Gaussian operations acting on bosonic quantum states. Depending on the input state and on the quality of the channel, the output suffers certain amount of noise. For a long time it has been conjectured, but never proved, that output states of Gaussian channels corresponding to coherent input signals are the less noisy ones (in the sense of a majorization criterion). In this work we prove this conjecture. Specifically we show that every output state of a phase insensitive Gaussian channel is majorized by the output state corresponding to a coherent input. The proof is based on the optimality of coherent states for the minimization of strictly concave output functionals. Moreover we show that coherent states are the unique optimizers.Comment: 7 pages, 1 figure. Published versio

Optimal fidelity of teleportation of coherent states and entanglement

We study the Braunstein-Kimble protocol for the continuous variable teleportation of a coherent state. We determine lower and upper bounds for the optimal fidelity of teleportation, maximized over all local Gaussian operations for a given entanglement of the two-mode Gaussian state shared by the sender (Alice) and the receiver (Bob). We also determine the optimal local transformations at Alice and Bob sites and the corresponding maximum fidelity when one restricts to local trace-preserving Gaussian completely positive maps.Comment: 10 pages, 2 figure

Vandermonde-subspace Frequency Division Multiplexing for Two-Tiered Cognitive Radio Networks

Vandermonde-subspace frequency division multiplexing (VFDM) is an overlay spectrum sharing technique for cognitive radio. VFDM makes use of a precoder based on a Vandermonde structure to transmit information over a secondary system, while keeping an orthogonal frequency division multiplexing (OFDM)-based primary system interference-free. To do so, VFDM exploits frequency selectivity and the use of cyclic prefixes by the primary system. Herein, a global view of VFDM is presented, including also practical aspects such as linear receivers and the impact of channel estimation. We show that VFDM provides a spectral efficiency increase of up to 1 bps/Hz over cognitive radio systems based on unused band detection. We also present some key design parameters for its future implementation and a feasible channel estimation protocol. Finally we show that, even when some of the theoretical assumptions are relaxed, VFDM provides non-negligible rates while protecting the primary system.Comment: 9 pages, accepted for publication in IEEE Transactions on Communication

Entanglement in fermionic systems

The anticommuting properties of fermionic operators, together with the presence of parity conservation, affect the concept of entanglement in a composite fermionic system. Hence different points of view can give rise to different reasonable definitions of separable and entangled states. Here we analyze these possibilities and the relationship between the different classes of separable states. We illustrate the differences by providing a complete characterization of all the sets defined for systems of two fermionic modes. The results are applied to Gibbs states of infinite chains of fermions whose interaction corresponds to a XY-Hamiltonian with transverse magnetic field.Comment: 13 pages, 3 figures, 4 table

Directly estimating non-classicality

We establish a method of directly measuring and estimating non-classicality - operationally defined in terms of the distinguishability of a given state from one with a positive Wigner function. It allows to certify non-classicality, based on possibly much fewer measurement settings than necessary for obtaining complete tomographic knowledge, and is at the same time equipped with a full certificate. We find that even from measuring two conjugate variables alone, one may infer the non-classicality of quantum mechanical modes. This method also provides a practical tool to eventually certify such features in mechanical degrees of freedom in opto-mechanics. The proof of the result is based on Bochner's theorem characterizing classical and quantum characteristic functions and on semi-definite programming. In this joint theoretical-experimental work we present data from experimental optical Fock state preparation, demonstrating the functioning of the approach.Comment: 4+1 pages, 2 figures, minor change

Trophic cascades in boreal landscapes: top predator protection on tree seedlings and forest grouse

Changes in the abundance of top predators have brought about notable, cascading effects in ecosystems around the world. In this thesis, I examined several potential trophic cascades in boreal ecosystems, and their separate interspecific interactions. The main aim of the thesis was to investigate whether predators in the boreal forests have direct or indirect cascading effects on the lower trophic levels. First, I compared the browsing effects of different mammalian herbivores by excluding varying combinations of voles, hares and cervids from accessing the seedlings of silver birch (Betula pendula), Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). Additionally, I studied the effect of simulated predation risk on vole browsing by using auditory cues of owls. Moving upwards on the trophic levels, I examined the intraguild interactions between the golden eagle (Aquila chrysaetos), and its mesopredator prey, the red fox (Vulpes vulpes) and the pine marten (Martes martes). To look at an entire potential trophic cascade, I further studied the combined impacts of eagles and mesopredators on the black grouse (Tetrao tetrix) and the hazel grouse (Tetrastes bonasia), predicting that the shared forest grouse prey would benefit from eagle presence. From the tree species studied, birch appears to be the most palatable one for the mammalian herbivores. I observed growth reductions in the presences of cervids and low survival associated with hares and voles, which suggests that they all weaken regeneration in birch stands. Furthermore, the simulated owl predation risk appeared to reduce vole browsing on birches in late summer, although the preferred grass forage is then old and less palatable. Browsing by voles and hares had a negative effect on the condition and survival of Scots pine, but in contrast, the impact of mammalian herbivores on spruce was found to be small, at least when more preferred food is available. I observed that the presence of golden eagles had a negative effect on the abundance of adult black grouse but a positive, protective effect on the proportion of juveniles in both black grouse and hazel grouse. Yet, this positive effect was not dependent on the abundance foxes or martens, nor did eagles seem to effectively decrease the abundance of these mesopredators. Conversely, the protection effect on grouse could arise from fear effects and also be mediated by other mesopredators. The results of this thesis provide important new information about trophic interactions in the boreal food webs. They highlight how different groups of mammalian herbivores vary in their effects on the growth and condition of different tree seedlings. Lowered cervid abundances could improve birch regeneration, which indirectly supports the idea that the key predators of cervids could cause cascading effects also in Fennoscandian forests. Owls seem to reduce vole browsing through an intimidation effect, which is a novel result of the cascading effects of owl vocalisation and could even have applications for protecting birch seedlings. In the third cascade examined in this thesis, I found the golden eagle to have a protective effect on the reproducing forest grouse, but it remains unclear through which smaller predators this effect is mediated. Overall, the results of this thesis further support the idea that there are cascading effects in the forests of Northern Europe, and that they are triggered by both direct and non‐lethal effects of predation.Muutokset suurpetojen runsaudessa ovat aiheuttaneet huomattavia heijastevaikutuksia ekosysteemeissä eri puolilla maailmaa. Tässä väitöskirjassa tarkastelin useita mahdollisia ravintoverkkojen sisäisiä kaskadivaikutuksia sekä lajienvälisiä vuorovaikutussuhteita pohjoisella havumetsävyöhykkeellä. Työni päätavoitteena oli tutkia, onko pohjoisten havumetsien pedoilla suoria tai epäsuoria heijastevaikutuksia ravintoverkon alemmille trofiatasoille. Ensiksi vertasin aitauskokeissa eri nisäkäs‐kasvinsyöjien laidunnusvaikutuksia puiden taimiin siten, että estin myyrien, jänisten tai hirvieläinten pääsyn syömään rauduskoivuja (Betula pendula), mäntyjä (Pinus sylvestris) sekä kuusia (Picea abies). Lisäksi tutkin simuloidun saalistusuhkan vaikutusta myyrien laidunnukseen pöllöjen ääntelyä käyttämällä. Seuraavaksi selvitin ylemmillä trofiatasoilla petokillan sisäisiä vuorovaikutussuhteita käyttäen tutkimuslajeina maakotkaa (Aquila chrysaetos) sekä tämän saaliiksi toisinaan joutuvia kettua (Vulpes vulpes) ja näätää (Martes martes). Tutkiakseni kokonaista trofiakaskadia, selvitin lisäksi maakotkan ja mainittujen pienpetojen yhteisvaikutuksia teeren (Tetrao tetrix) sekä pyyn (Tetrastes bonasia) populaatioihin. Ennusteena oli, että kotkan läsnäolo voisi hyödyttää näitä metsäkanalintuja. Tutkituista puulajeista koivu vaikutti olevan alttein nisäkäskasvinsyöjien laidunnukselle. Havaitsin, että hirvieläinten läsnä ollessa koivujen kasvunopeus hidastui, kun taas jänikset ja myyrät alensivat näiden taimien selviytymistä. Tämän perusteella kaikki kolme nisäkäsryhmää heikentävät uusiutumista koivutaimikoissa. Lisäksi havaitsin, että simuloitu pöllön saalistusuhka vaikutti vähentävän koivujen laidunnuspainetta loppukesästä, vaikka tuolloin myyrien suosima ruoho on vanhaa ja vähemmän maittavaa. Myyrien ja jänisten laidunnuksella oli haitallinen vaikutus männyntaimien kasvuun ja kuntoon, mutta sen sijaan kuusentaimiin eivät nisäkäskasvinsyöjät juurikaan vaikuttaneet, ainakaan oloissa joissa vaihtoehtoista ravintoa on myös saatavilla. Havaitsin että maakotkan läsnäolo vähensi teeren runsautta, mutta toisaalta lisäsi poikasten osuutta sekä teeren että pyyn populaatioissa. Tämä maakotkan suotuisa suojeluvaikutus ei kuitenkaan ollut riippuvainen ketun tai näädän runsaudesta, eikä maakotka vähentänyt näiden pienpetojen lukumääriä. Sen sijaan kanalintuihin ulottuva suojeluvaikutus voi johtua kotkan aiheuttamasta pelotteesta ja sen välittäjänä voivat toimia myös muut pienpedot. Tämän väitöskirjan tulokset tarjoavat uutta, tärkeää tietoa pohjoisen havumetsävyöhykkeen ravintoverkoista. Ne korostavat sitä, miten eri nisäkäskasvinsyöjillä voi olla vaihtelevia vaikutuksia eri puulajien kasvuun ja kuntoon. Hirvieläinten vähentyminen voisi parantaa koivikoiden uudistumista, mikä epäsuorasti tukee ajatusta siitä, että hirvieläinten tärkeimmät pedot voisivat runsastuessaan aiheuttaa heijastevaikutuksia myös Fennoskandian metsissä. Pöllöt näyttävät vähentävän myyrien laidunnusta pelotevaikutuksen kautta, mikä on uusi löydös pöllöjen ääntelyn kaskadivaikutuksista, jota voidaan jopa soveltaa koivutaimikoiden suojaamisessa. Tarkastellessani väitöskirjani kolmatta trofiakaskadia havaitsin, että maakotkalla on suojeluvaikutus metsäkanalintuihin, joskin epäselväksi jää, minkä petolajien kautta tämä vaikutus välittyy. Kaiken kaikkiaan tämän väitöskirjan tulokset antavat lisää tukea ajatukselle, että Pohjois‐Euroopan metsissä esiintyy trofiakaskadeja, ja että ne lähtevät liikkeelle sekä petojen suorista saalistusvaikutuksista että epäsuorista pelotevaikutuksista.Siirretty Doriast

Challenges and possibilities in telecare: Realist evaluation of a Norwegian telecare project

This thesis reports from a telecare evaluation in a Norwegian municipality (2012-2016). The project was established to provide domestic results from a hitherto new field in the country to underpin future policy. This evaluation includes pre- and post-implementation data collection, which has been scarce in telecare. The methodological approach was realist evaluation that seeks to explore how telecare works, for whom, why and in which circumstances – or why it does not work. The research aimed to explore the hypothesis elicited from national policy documents: ‘If telecare is used, then people are enabled to remain safe in their own home for longer’. Various methods were used to gather data from multiple stakeholders as they have different knowledge about how the implementation developed. The methods in this evaluation included literature reviews, observations, and sequential interviews with users and relatives in addition to sequential focus groups with frontline staff. Realist evaluation was particularly suitable in demonstrating how and why telecare is useful to some users but not to others. Telecare had to match users’ abilities and needs for them to benefit from it. Telecare operates in a dynamic context, and therefore requires adjustment according to the user’s current situation, taking into account changes as they occur. This appears to have been often underestimated. Telecare holds a different position from other devices and technologies in people’s everyday life, which also needs to be acknowledged. Correct assessment is significant for users to obtain the intended effect from telecare. When telecare is correctly adjusted to users, it increases safety, which is essential for enabling older people to remain living at home. Several challenges in establishing telecare projects are identified and alternative ways to understand multi-disciplinary partnerships are suggested. By using realist evaluation the findings are nuanced and point to elements that are significant for achieving the intended outcomes