A. Borghese

A. Borghese
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A. Borghese
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High Energy Physics - Theory (10)
 
High Energy Astrophysical Phenomena (4)
 
High Energy Physics - Phenomenology (1)
 
Cosmology and Nongalactic Astrophysics (1)
 
Solar and Stellar Astrophysics (1)

Publications Authored By A. Borghese

We report on the results of a detailed phase-resolved spectroscopy of archival XMM--Newton observations of X-ray Dim Isolated Neutron Stars (XDINSs). Our analysis revealed a narrow and phase-variable absorption feature in the X-ray spectrum of RX J1308.6+2127. Read More

In search for the counterpart to the Fermi-LAT source 3FGL J0838.8-2829, we report on 1) a new magnetic Cataclysmic Variable (mCV), RX J0838-2827, that we identify as an asynchronous system (therefore not associated with this Fermi-LAT source) and 2) on a new X-ray flaring source, XMM J083850.4-282759, that might be tentatively identified as new candidate Transitional Millisecond Pulsar, possibly associated with the gamma-ray source. Read More

The 6.67 hr periodicity and the variable X-ray flux of the central compact object (CCO) at the center of the SNR RCW 103, named 1E 161348-5055, have been always difficult to interpret within the standard scenarios of an isolated neutron star or a binary system. On 2016 June 22, the Burst Alert Telescope (BAT) onboard Swift detected a magnetar-like short X-ray burst from the direction of 1E 161348-5055, also coincident with a large long-term X-ray outburst. Read More

2015Jun
Affiliations: 1U. Amsterdam, 2U. Amsterdam/CSIC-IEEC, 3U. Insubria/U. Amsterdam/INAF, 4IUSS-Pavia/INAF, 5U. Padova/MSSL

We present the discovery of a strongly phase-variable absorption feature in the X-ray spectrum of the nearby, thermally-emitting, isolated neutron star RX J0720.4-3125. The absorption line was detected performing detailed phase-resolved spectroscopy in 20 XMM-Newton observations, covering the period May 2000 - September 2012. Read More

Gauged N=8 supergravity in four dimensions is now known to admit a deformation characterized by a real parameter $\omega$ lying in the interval $0\le\omega\le \pi/8$. We analyse the fluctuations about its anti-de Sitter vacuum, and show that the full N=8 supersymmetry can be maintained by the boundary conditions only for $\omega=0$. For non-vanishing $\omega$, and requiring that there be no propagating spin s>1 fields on the boundary, we show that N=3 is the maximum degree of supersymmetry that can be preserved by the boundary conditions. Read More

In this paper we search for accelerating power-law solutions and ekpyrotic solutions within minimal and maximal four dimensional supergravity theories. We focus on the STU model for N=1 and on the new CSO(p,q,r) theories, which were recently obtained exploiting electromagnetic duality, for N=8. In the minimal case we find some new ekpyrotic solutions, while in the maximal case we find some new generic power-law solutions. Read More

While electromagnetic duality is a symmetry of many supergravity theories, this is not the case for the N=8 gauged theory. It was recently shown that this rotation leads to a one-parameter family of SO(8) supergravities. It is an open question what the period of this parameter is. Read More

We describe recent developments regarding gauged N=8 supergravity in D=4. Using the embedding tensor formulation we show how to classify all the extrema of this theory with a G2 residual gauge symmetry. Our classification contains all the vacua of the recently discovered family of SO(8) gauged maximal supergravities. Read More

We investigate the SU(3)-invariant sector of the one-parameter family of SO(8) gauged maximal supergravity that has been recently proposed. To this end, we construct the N=2 truncation of this theory and analyse its full vacuum structure. The number of critical point is doubled and includes new N=0 and N=1 branches. Read More

We perform an exhaustive classification of G_2 invariant extrema of the most general gauged N=8 supergravity in four dimensions. They comprise four branches of Anti-de Sitter solutions labelled by a single parameter. Interestingly, while the gauge groups vary with the parameters, the mass spectra are invariant. Read More

We construct a one-parameter family of five-dimensional N=2 supergravity Lagrangians with an SU(2,1) / U(2) hypermultiplet. For certain values of the parameter, these are argued to describe the dynamics of scalar modes of superstrings on AdS_5 x T^{1,1}, and therefore to be dual to specific chiral primary operators of Klebanov-Witten superconformal field theory. We demonstrate that, below a critical temperature, the thermodynamics is dominated by charged black holes with hair for the scalars that are dual to the operator of lowest conformal dimension 3/2. Read More

We discuss a general bound on the possibility to realise inflation in any minimal supergravity with F-terms. The derivation crucially depends on the sGoldstini, the scalar field directions that are singled out by spontaneous supersymmetry breaking. The resulting bound involves both slow-roll parameters and the geometry of the K\"ahler manifold of the chiral scalars. Read More

Recently, it has been shown that maximal supergravity allows for non-supersymmetric AdS critical points that are perturbatively stable. We investigate this phenomenon of stability without supersymmetry from the sGoldstino point of view. In particular, we calculate the projection of the mass matrix onto the sGoldstino directions, and derive the necessary conditions for stability. Read More

We consider the stability of non-supersymmetric critical points of general N=4 supergravities. A powerful method to analyse this issue based on the sGoldstino direction has been developed for minimal supergravity. We adapt this to the present case, and address the conceptually new features arising for extended supersymmetry. Read More