Abstract:
The creation of universes in entangled pairs may avoid the initial singularity and it would have observable consequences in a large macroscopic universe like ours, at least in principle. In this paper we describe the creation of an entangled pair of universes from a double instanton, which avoids the initial singularity, in the case of a homogeneous and isotropic universe with a conformally coupled massless scalar field. The thermodynamical properties of interuniversal entanglement might have observable consequences on the properties of our single universe provided that the thermodynamics of entanglement is eventually related to the classical formulation of thermodynamics. 1. Introduction From the very beginning of human knowledge the creation of the universe has been one of the most exciting, fundamental, and intriguing questions of natural philosophy. In contemporary science, it has been the prime feature of quantum cosmology and it is profoundly related to the existence of space-time singularities and the need of a quantum theory of gravity that would presumably explain or avoid them. In quantum cosmology, the birth of the universe is deeply related to the boundary conditions that we impose on the state of the universe. Different boundary conditions have been proposed in the literature [1–9]. Among them, two main proposals have become customary in quantum cosmology: the Hartle-Hawking no boundary proposal [1, 2, 10] and the Vilenkin tunneling proposal [3, 4, 11]. In both cases, the universe is said to be created from nothing, where by nothing we should not understand the absolute meaning of nothing, that is, something to which we can ascribe no properties, but rather a classically forbidden region of the space-time where space, matter, and above all time do not physically exist as such. The boundary conditions to be imposed on the state of the universe have usually been considered of metaphysical nature and its choice thus a sort of taste. Some particular proposal [5, 12] has claimed to be preferable in order to have a suitable long enough inflationary stage of the universe that would explain the observed homogeneity and isotropy. However, counter-arguments have also been given [13–16]. The main problem for an observational choice of the boundary conditions of the universe is that the rapid expansion of the inflationary period would erase any trace of the preinflationary stage of the universe [12]. Besides, the question would be more unsettled than ever if the results of the Planck mission [17, 18] eventually disfavor typical models of inflation

Abstract:
Quantum information theory and the multiverse are two of the greatest outcomes of the XX century physics. The consideration of entanglement between the quantum states of two or more universes in a multiverse scenario provides us with a completely new paradigm that opens the door to novel approaches for traditionally unsolved problems in cosmology. More precisely, the problems of the cosmological constant, the arrow of time and the choice of boundary conditions, among others. It also encourages us to adopt new points of view about major philosophical ideas. In this chapter, we shall present the main features that may characterize inter-universal entanglement and it will be addressed the customary problems of cosmology from the new perspective that the quantum multiverse scenario supplies us with. In summary, the appropriate boundary condition that has to be imposed on the quantum state of the whole multiverse allows us to interpret it as made up of entangled pairs of universes. Then, a quantum thermodynamical description of single universes can be given and it can be shown that it may induce observable effects in the energy properties of the Universe. The effects that the boundary condition of the multiverse has on the vacuum energy and the arrow of time of single universes are also studied. As a consequence of inter-universal entanglement, the former might be discriminated from observational data and the latter would favor the growth of cosmic structures that increase the amount of local entropy mainly in the very early phase of the universe. All these characteristics of inter-universal entanglement would eventually impel us to develop the concept of the physical multiverse, one for which the theory could be not only fallible but also indirectly observed.

Abstract:
In this paper, the model of a multiverse made up of entangled pairs of
universes is presented. The arrow of time obtained from the principles of
thermodynamics and the arrow of time given by the thermodynamics of entanglement
for single universes are analyzed. The latter requires that the single
universes expand once they have crossed the quantum barrier at the Euclidean
regime. The possible relationship with respect to the growth of local
structures in a single universe is also discussed.

Abstract:
Inter-universal entanglement may even exist in a multiverse in which there is no common space-time among the universes. In particular, the entanglement between the expanding and contracting branches of the universe might have observable consequences in the dynamical and thermodynamical properties of one single branch, making therefore testable the whole multiverse proposal, at least in principle.

Abstract:
The third quantization formalism of quantum cosmology adds simplicity and conceptual insight into the quantum description of the multiverse. Within such a formalism, the existence of squeezed and entangled states raises the question of whether the complementary principle of quantum mechanics has to be extended to the quantum description of the whole space-time manifold. If so, the 'particle' description entails the consideration of a multiverse scenario and the 'wave' description induces us to consider as well correlations and interactions among the universes of the multiverse.

Abstract:
Using the known result that the nucleation of baby universes in correlated pairs is equivalent to spacetime squeezing, we show in this letter that there exists a T-duality symmetry between two-dimensional warp drives, which are physically expressible as localized de Sitter little universes, and two dimensional Tolman-Hawking and Gidding-Strominger baby universes respectively correlated in pairs, so that the creation of warp drives is also equivalent to spacetime squeezing. Perhaps more importantly, it has been also seen that the nucleation of warp drives entails a violation of the Bell's inequalities, and hence the phenomena of quantum entanglement, complementarity and wave function collapse. These results are generalized to the case of any dynamically accelerating universe filled with dark or phantom energy whose creation is also physically equivalent to spacetime squeezing and to the violation of the Bell's inequalities, so that the universe we are living in should be governed by essential sharp quantum theory laws and must be a quantum entangled system.

Abstract:
The boundary conditions to be imposed on the quantum state of the whole multiverse could be such that the universes would be created in entangled pairs. Then, inter-universal entanglement would provide us with a vacuum energy for each single universe that might be fitted with observational data, making testable not only the multiverse proposal but also the boundary conditions of the multiverse. Furthermore, the second law of the entanglement thermodynamics would enhance the expansion of the single universes.

Abstract:
In this paper we study the accretion of dark energy onto a black hole in the cases that dark energy is equipped with a positive cosmological constant and when the space-time is described by a Schwarzschild-de Sitter metric. It is shown that, if confronted with current observational data, the results derived when no cosmological constant is present are once again obtained in both cases.

Abstract:
The pseudo-Frobenius numbers of a numerical semigroup are those gaps of the numerical semigroup that are maximal for the partial order induced by the semigroup. We present a procedure to detect if a given set of integers is the set of pseudo-Frobenius numbers of a numerical semigroup and, if so, to compute the set of all numerical semigroups having this set as set of pseudo-Frobenius numbers.

Abstract:
objectives: to report one case of renal trauma in a patient with horseshoe kidney treated conservatively by superselective embolization. methods: we report the case of a 19 year old male presenting at the emergency room with macroscopic hematuria and severe abdominal pain after a motor vehicular accident. results: iv contrast ct scan showed a horseshoe kidney with a fracture in the area between the lower pole of the left kidney and the isthmus, with active bleeding and a big retroperitoneal hematoma extended to pelvis. retarded exams showed contrast extravasation compatible with significant urinoma. renal arteriography was performed, showing a double renal pedicle on each kidney and a common caudal lumbar-renal trunk giving accessory branches to both kidneys？ lower poles and contrast extravasation compatible with active bleeding. the lumbar-renal trunk was selectively catheterized reaching the left kidney and isthmus branches which were embolized. retrograde catheterization of the urinary tract with a straight ureteral catheter was performed to facilitate drainage of the urinoma. this catheter was subsequently removed after control ct scan showing complete resolution of the urinoma and no bleeding. control ct scan three months after embolization demonstrated complete resolution of the hematoma. no late complications appeared. renal function and blood pressure have been completely normal after 12 months of follow-up. conclusions: horseshoe kidney is a rare congenital malformation. this clinical case demonstrates that conservative treatment is a still the gold standard treatment for renal trauma, even in kidneys with congenital anomalies.