2,865 research outputs found
Nonlocal quantum field theory without acausality and nonunitarity at quantum level: is SUSY the key?
The realization of a nonlocal quantum field theory without losing unitarity,
gauge invariance and causality is investigated. It is commonly retained that
such a formulation is possible at tree level, but at quantum level acausality
reappears at one loop. We suggest the the problem of acausality is, in a broad
sense, similar to the one about anomalies in quantum field theory. By virtue of
this analogy, we suggest that acausal diagrams resulting from the fermionic
sector and the bosonic one might cancel each other, with a suitable content of
fields and suitable symmetries. As a simple example, we show how supersymmetry
can alleviate this problem in a simple and elegant way, i.e., by leading to
exact cancellations of harmful diagrams, to all orders of perturbation theory,
in the case of a nonlocal Wess-Zumino model. On the other hand, the same is
true for a super Yang-Mills model, but in this case, other important acausal
diagrams are also originating from supersymmetric D-terms. As a consequence, we
conjecture that, for a generic gauge theory, an infinite number of superfields
are needed in order to obtain a complete cancellation between all diagrams.
This framework is naturally occurring in string theory, where infinite
Kaluza-Klein towers of higher-spin fields are generally predicted.Comment: Supergraphs reformulation in non-local case are added, with a formal
derivation of these. More explicit calculations, in main interesting one-loop
processes, are explicitly shown. More comments and references. Main results
and Conclusions remain the sam
Industrial symbiosis: anaerobic digestion of waste products as mitigation strategy
La simbiosi industriale è una strategia aziendale con la quale è possibile aumentare la sostenibilità dei processi produttivi. La partnership tra un’azienda vinicola e una società energetica ha consentito un’innovazione di processo che consente il riutilizzo dei rifiuti alimentari dalla produzione del vino. L’azienda vinicola produce 5.200.000 tonnellate di uva. Con un biodigestore è possibile reinserire nel ciclo produttivo circa 220.000 tonnellate di rifiuti alimentari, composti da: rifiuti vegetali, trucioli di legno e rifiuti da potatura. Il riutilizzo degli scarti di produzione genera 105.000 MWh di calore e 81.000 MWh di energia elettrica, con un risparmio di 35.000 tonnellate di CO2 . I risultati ottenuti possono essere ottenuti dalle aziende alimentari che richiedono un elevato fabbisogno energetico e che producono notevoli quantità di rifiuti organici.Industrial symbiosis is a business strategy through which it is possible increase the sustainability of production processes. The partnership between a winery and an energy company has enabled the implementation of a production innovation that allows the upgrading by food waste from wine production. The winery produces 5,200,000 tons of grapes. Through the creation of a biodigester it is possible to re-enter in the production cycle about 220,000 tons of food waste, consisting of: vegetable waste, wood chips and waste from pruning. The reuse of production waste can generate 105,000 MWh of heat and 81,000 MWh of electrical energy, allowing savings of 35,000 tons of CO2 . The results obtained could be reached by food manufacturers that require a high energy needs and that produce significant amounts of organic waste
Sustainability of technological innovation investiments. Photovoltaic panels case study
as photovoltaic panels. In the case study analysed are shown the benefits
obtained from the investments of the central Italy after installing photovoltaic systems.
The total expenditure for the electricity purchase is € 52.326, while the total benefit of
the investment is € 18.789, equal in percentage to a 53% energy saving over a period
of 20 years. The company expeniture in the absence of a photovoltaic system is equal
to € 109.03, while in the presence of a plant, considering also all costs incurred for €
93.090, with a percentage of profit on the investment made equal to almost 15% in 20
years
The variable X-ray emission of PSR B0943+10
The old pulsar PSR B0943+10 (P=1.1 s, characteristic age tau=5 Myr) is the
best example of mode-switching radio pulsar. Its radio emission alternates
between a highly organized state with regular drifting subpulses (B mode) and a
chaotic emission pattern (Q mode). We present the results of XMM-Newton
observations showing that the X-ray properties of PSR B0943+10 depend on its
radio state (Hermsen et al. 2013). During the radio fainter state (Q mode) the
X-ray flux is more than a factor two larger than during the B-mode and X-ray
pulsations with about 50% pulsed fraction are detected. The X-ray emission of
PSR B0943+10 in the B-mode is well described by thermal emission with blackbody
temperature kT=0.26 keV coming from a small hot spot with luminosity of 7x10^28
erg/s, in good agreement with the prediction of the partially screened gap
model, which also explains the properties of the radio emission in this mode.
We derived an upper limit of 46% on the X-ray pulsed fraction in the B-mode,
consistent with the geometry and viewing angle of PSR B0943+10 inferred from
the radio data. The higher flux observed during the Q-mode is consistent with
the appearance of an additional component with a power-law spectrum with photon
index 2.2. We interpret it as pulsed non-thermal X-rays produced in the star
magnetosphere. A small change in the beaming pattern or in the efficiency of
acceleration of the particles responsible for the non-thermal emission can
explain the reduced flux of this component during the radio B-mode.Comment: Accepted for publication in MNRA
X-ray emission from hot subdwarfs with compact companions
We review the X-ray observations of hot subdwarf stars. While no X-ray
emission has been detected yet from binaries containing B-type subdwarfs,
interesting results have been obtained in the case of the two luminous O-type
subdwarfs HD 49798 and BD +37 442. Both of them are members of binary systems
in which the X-ray luminosity is powered by accretion onto a compact object: a
rapidly spinning (13.2 s) and massive (1.28 M_sun) white dwarf in the case of
HD 49798 and most likely a neutron star, spinning at 19.2 s, in the case of BD
+37 442. Their study can shed light on the poorly known processes taking place
during common envelope evolutionary phases and on the properties of wind mass
loss from hot subdwarfs.Comment: To be published in the proceedings of the 40th Liege International
Astrophysical Colloquium "Ageing low mass stars: from red giants to white
dwarfs
L’eco-efficienza dei contenitori di vetro sottile
La valutazione economica della produzione sostenibile dei contenitori di vetro dimostra che l’assottigliamento dei contenitori e il loro riciclo comporta vantaggi ambientali immediatamente quantificabili.Economic assessment of the sustainable production of glass containers shows that making the containers thinner and recycling them carries immediately quantifiable environmental advantages
Search for X-ray emission from subdwarf B stars with compact companion candidates
Stellar evolutionary models predict that most of the early type subdwarf
stars in close binary systems have white dwarf companions. More massive
companions, such as neutron stars or black holes, are also expected in some
cases. The presence of compact stars in these systems can be revealed by the
detection of X-rays powered by accretion of the subdwarf's stellar wind or by
surface thermal emission. Using the Swift satellite, we carried out a
systematic search for X-ray emission from a sample of twelve subdwarf B stars
which, based on optical studies, have been suggested to have degenerate
companions. None of our targets was detected, but the derived upper limits
provide one of the few observational constraints on the stellar winds of early
type subdwarfs. If the presence of neutron star companions is confirmed, our
results constrain the mass loss rates of some of these subdwarf B stars to
values <10^{-13}-10^{-12} Msun/yr.Comment: Accepted for publication in Astronomy and Astrophysic
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