617 research outputs found
On the fractal dimension of orbits compatible with the Tsallis statistics
No full textIn a previous paper [A. Carati, Physica A 348 (2005) 110-120] it was shown how, for a dynamical system, the probability distribution function of sojourn-times in phase-space, defined in terms of the dynamical orbits (up to a given observation time), induces unambiguously a statistical ensemble in phase-space. In the present paper, the p.d.f. of the sojourn-times corresponding to a Tsallis ensemble is obtained (this, by the way, requires the solution of a problem of a general character, disregarded in paper [A. Carati, Physica A 348 (2005) 110-120]). In particular some qualitative properties, such as the fractal dimension, of the dynamical orbits compatible with the Tsallis ensembles are indicated
Sharing sovereignty : building democracy by external intervention
No full textThis analysis suggests the idea that
shared sovereignty and neotrusteeships
are the result of the
paradoxes entailed by the promotion
of democracy by external
intervention. The goal of
democratization and the democratic
attitude of recent international
interventions lead to some
contradictory principles, particularly
between the respect of selfdetermination
and external control
and between temporary engagement
and protracted international
interference.
These contradictions affect the
international administrators’
activities in the target-country. While
they tend to concede powers to
local political leaders in the light of
the self-determination principle, they
hold some essential power in order
to foster the transition to
democracy. While they are inclined
to give back full independence, their
prolonged presence is required to
guarantee the process of
democratization. The result is a
balance between international and
local power prerogatives which ends
up in a de facto shared-sovereignt
Definitely Maybe : What's the Real Obama Signature on US Defence Policies?
No full textSeveral challenges that Obama faced in his first four years in office remain at the top of his agenda. Yet, the circumstances in which they are to be met are considerably changed. Obama’s second term foreign policy is suffering from a number of domestic and international constraints: The American public is tired of war, the economic slow-down leads to severe cuts on defense budget, austerity in Europe is negatively affecting NATO international commitment and Obama's support abroad and at home is lessened.
This paper explores how the Obama administration is coping with these constraints. It focuses on elements of evolution and continuity in U.S. foreign and security policies in four policy area: (a) strategic planning; (b) the strategic shift toward Asia; (c) mission in Afghanistan; and (d) war on terrorism and the use of drones
On the definition of temperature using time-averages
No full textThis paper is a natural continuation of a previous one by the author, which was concerned with the foundations of statistical thermodynamics far from equilibrium. One of the problems left open in that paper was the correct definition of temperature. In the literature, temperature is in general defined through the mean kinetic energy of the particles of a given system. In this paper, instead, temperature is defined A la Caratheodory, the system being coupled to a heat bath, and temperature being singled out as the "right" integrating factor of the exchanged heat. As a byproduct, the "right" expression for the entropy is also obtained. In particular, in the case of a q-distribution the entropy turns out to be that of Tsallis
Chaoticity threshold in magnetized plasmas : numerical results in the weak coupling regime
No full textThe present paper is a numerical counterpart to the theoretical work [Carati et al., Chaos 22, 033124 (2012)]. We are concerned with the transition from order to chaos in a one-component plasma (a system of point electrons with mutual Coulomb interactions, in a uniform neutralizing background), the plasma being immersed in a uniform stationary magnetic field. In the paper [Carati et al., Chaos
22, 033124 (2012)], it was predicted that a transition should take place when the electron density is increased or the field decreased in such a way that the ratio between plasma and cyclotron frequencies becomes of order 1, irrespective of the value of the so-called Coulomb coupling parameter. Here, we perform numerical computations for a first principles model of N point
electrons in a periodic box, with mutual Coulomb interactions, using as a probe for chaoticity the time-autocorrelation function of magnetization. We consider two values of Coulomb coupling parameter (0.04 and 0.016) in the weak coupling regime, with N up to 512. A transition is found to occur for ratio between plasma and cyclotron frequencies in the range between 0.25 and 2, in fairly good agreement with the theoretical prediction. These results might be of interest for the problem of the breakdown of plasma confinement in fusion machines
Trump’s Legacy and the Liberal International Order: Why Trump Failed to Institutionalise an Anti-global Agenda
No full textDonald Trump was expected to repeal the internationalist approach that had dominated US foreign policy since the end of the Second World War, but his impact was narrower than is commonly supposed. On the one hand, the problems of the liberal international order predate Trump and probably will outlive his presidency. He was more a symptom than the cause of those difficulties, thus his responsibilities should not be overstated. On the other hand, despite several renegotiations and accusations against its partners, the US involvement in multilateral organisations remains solid and its engagement overseas remarkable. Overall, Trump’s performance in shifting US foreign policy toward an anti-globalist stance was quite poor. Contrary to mainstream accounts of Trump’s foreign policy, the president’s revisionism has arguably been thwarted less by the internationalist approach within the foreign policy establishment than by his own personality and his policy-making attitudes
An extension of Eliezer's theorem on the Abraham-Lorentz-Dirac equation
No full textIn 1943 Eliezer showed that, according to the Abraham-Lorentz-Dirac equation, a point charge cannot fall on a centre of attractive Coulombian forces, if one considers only motions constrained on a line. In other words, the Abraham-Lorentz-Dirac equation on a line does not admit solutions x(t) such that x → 0 for t → tc, with either a finite or infinite tc. In this paper it is shown that this remain true for the full three-dimensional problem
Responsibility to protect, NATO and the problem of who should intervene : reassessing the intervention in Libya
No full textOne of the most challenging issues concerning the doctrine of the
Responsibility to Protect (R2P) is ‘who should intervene’ in case of
gross violations of human rights. After the intervention in Kosovo in
1999, the North Atlantic Treaty Organization (NATO) has been
increasingly considered a legitimate actor to fulfil the duty to
intervene for humanitarian reasons. In 2011, the first military
intervention inspired by the R2P in Libya reinforced the
appreciation of NATO as a viable enforcer of the doctrine. The
paper problematizes the idea that NATO could be a straightforward
solution to the problem of who should intervene. NATO’s
constitutive nature comprises aspects that are at odds with R2P as
a normative scheme. In this regard, the paper delves into three
aspects: (a) the controversial issue of ‘delegated authority’ from the
UN to NATO; (b) the tension between the universalistic character of
the R2P and the particularistic nature of NATO and (c) the military
nature of the alliance and its consequent focus on security/military
considerations that rarely, or just occasionally, match with
humanitarian concerns. Finally, the paper analyses the intervention
in Libya assessing the incongruities between NATO’s military
operations and the normative framework of R2P
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