Spontaneously Broken Symmetries

The phenomenon of spontaneous symmetry breaking is a common feature of phase transitions in both classical and quantum physics. In a first part we study this phenomenon for the case of a global internal symmetry and give a simple proof of Goldstone’s theorem. We show that a massless excitation appears, corresponding to every generator of a spontaneously broken symmetry. In a second part we extend these ideas to the case of gauge symmetries and derive the Brout–Englert–Higgs mechanism. We show that the gauge boson associated with the spontaneously broken generator acquires a mass and the corresponding field, which would have been the Goldstone boson, decouples and disappears. Its degree of freedom is used to allow the transition from a massless to a massive vector field.

Sensitivity of the SHiP experiment to dark photons decaying to a pair of charged particles

Dark photons are hypothetical massive vector particles that could mix with ordinary photons. The simplest theoretical model is fully characterised by only two parameters: the mass of the dark photon m$$_{\gamma ^{\mathrm {D}}}$$ γ D and its mixing parameter with the photon, $$\varepsilon $$ ε . The sensitivity of the SHiP detector is reviewed for dark photons in the mass range between 0.002 and 10 GeV. Different production mechanisms are simulated, with the dark photons decaying to pairs of visible fermions, including both leptons and quarks. Exclusion contours are presented and compared with those of past experiments. The SHiP detector is expected to have a unique sensitivity for m$$_{\gamma ^{\mathrm {D}}}$$ γ D ranging between 0.8 and 3.3$$^{+0.2}_{-0.5}$$ - 0.5 + 0.2 GeV, and $$\varepsilon ^2$$ ε 2 ranging between $$10^{-11}$$ 10 - 11 and $$10^{-17}$$ 10 - 17 .

Vector fields localization on brane worlds

To confine vector bosons in the four dimensional sector of a domain wall spacetime, we propose a mechanism in which the interaction among vectors is propagated via the self-interaction of the scalar wall. In the process, the vector acquires an asymptotic mass, defined by the bulk cosmological constant, and it ends up coupled to the wall by the tension of the brane. The mechanism is applied on the Randall Sundrum scenario and regular versions of it, and on singular domain walls. In any case, the electrostatic potential between two charged particles is defined by both the vector state attached to the wall and a continuous tower of massive vector states that propagate freely along the scenario's extra dimension.

Completely dark photons from gravitational particle production during the inflationary era

Starting with the de Broglie-Proca Lagrangian for a massive vector field, we calculate the number density of particles resulting from gravitational particle production (GPP) during inflation, with detailed consideration to the evolution of the number density through the reheating. We find plausible scenarios for the production of dark-photon dark matter of mass in a wide range, as low as a micro-electron volt to 1014 GeV. Gravitational particle production does not depend on any coupling of the dark photon to standard-model particles.

On the coupling of vector fields to the Gauss-Bonnet invariant

Inflationary models including vector fields have attracted a great deal of attention over the past decade. Such an interest owes to the fact that they might contribute to, or even be fully responsible for, the curvature perturbation imprinted in the cosmic microwave background. However, the necessary breaking of the vector fields conformal invariance during inflation is not without problems. In recent years, it has been realized that a number of instabilities endangering the consistency of the theory arise when the conformal invariance is broken by means of a non-minimal coupling to gravity. In this paper, we consider a massive vector field non-minimally coupled to gravity through the Gauss-Bonnet invariant, and investigate whether the vector can play the role of a curvaton while evading the emergence of instabilities and preserves the large-scale isotropy.

Persamaan Gelombang Gravitasi untuk Teori Proca yang Digeneralisasi

<p class="AbstractEnglish"><strong>Abstract:</strong> The direct detection of gravitational waves from binary black holes and neutron stars have been taking a new oportunities to test teori of gravity.The gravitational wave is affected by the modification of a gravity theory during propagation at cosmological distances. By comparing general equation of gravtiational wave and modification of gravity theory, is obtained equation of gravitational wave for the generalized Proca theories. As a result, we find equation of gravitational wave for the generalized Proca theory. We conclude that the massive vector field affected propagation of gravitational wave. we can use the result to test the generalized Proca theory. </p><p class="AbstrakIndonesia"><strong>Abstrak:</strong> Dengan terdeteksinya gelombang gravitasi secara langsung dari biner lubang hitam dan bintang neutron menjadi kesempatan untuk dapat menguji teori gravitasi yang sedang dikembangkan.Gelombang gravitasi secara umum dipengaruhi oleh modifikasi teori gravitasi selama penjalarannya pada jarak kosmologi. Dengan membandingkan persamaan gelombang gravitasi dengan teori modifikasi yang dikembangkan, diperoleh persamaan umum gelombang gravitasi dari teori gravitasi yang dikembangkan. Pada artikel ini diperoleh persamaan gelombang gravitasi untuk teori Proca yang digeneralisasi. Dapat disimpulkan bahwa fungsi yang mengandung vektor medan masif dapat mempengaruhi gelombang gravitasi. Persamaan ini dapat digunakan untuk menguji teori Proca yang digeneralisasi.</p>