Q-Stars in Anti de Sitter Spacetime

2015

Gen Relativ Gravit

We study boson stars in a theory of complex scalar field coupled to Einstein gravity with the potential: V (|Φ|) := m 2 |Φ| 2 + 2λ |Φ| (where m 2 and λ are positive constant parameters). This could be considered either as a theory of massive complex scalar field coupled to gravity in a conical potential or as a theory in the presence of a potential which is an overlap of a parabolic and a conical potential. We study our theory with positive as well as negative values of the cosmological constant Λ . Boson stars are found to come in two types, having either ball-like or shell-like charge density. We have studied the properties of these solutions and have also determined their domains of existence for some specific values of the parameters of the theory. Similar solutions have also been obtained by Hartmann, Kleihaus, Kunz, and Schaffer, in a V-shaped scalar potential.Keywords Gravity Theories · Boson stars · Boson shells · Q-balls · Q-shells A study of boson shells and boson stars in scalar electrodynamics with a self-interacting complex scalar field Φ coupled to Einstein gravity is of a very wide interest in the gravity theories[1]- [26] . Hartmann, Kleihaus, Kunz, and Schaffer (HKKS) [2,3] have recently studied boson stars in a theory of complex scalar field coupled to Einstein gravity in a V-shaped scalar potential: V (ΦΦ * ) ≡ V (|Φ|) = λ c |Φ| (where λ c is a constant). They have found that the boson stars come in two types, having either ball-like or shell-like charge density. They have studied the properties of these solutions and have also determined their domains of existence.Actually, the boson stars represent localized self-gravitating solutions [6,7,8], that have been considered in many different contexts [9,10,11,12,13]. To obtain boson stars, typically a complex scalar field Φ is considered. The U(1) invariance of the theory then provides a conserved Noether current.The properties of the boson stars depend strongly on the self-interaction employed. In particular, as discussed by Lee and collaborators [14] and by Coleman [15], the existence of a flat space-time limit of these localized solutions, i.e., the existence of Q-balls, puts constraints on the types of self-interaction possible.Arodz and Liz showed, that besides Q-balls another type of localized solution could also arise in flat space, when a V-shaped self-interaction is employed in the presence of a gauge field [16,17,18]. In this type of solution, the energy density is no longer ball-like as in the case of Q-balls, but it is instead shell-like.

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confidence: 72%

Boson stars in a theory of complex scalar field coupled to gravity

2015

Gen Relativ Gravit

“…Boson stars and boson shells representing the localized self-gravitating solutions were introduced long ago [1-3] and they have been studied vary widely in the literature . Such theories are being considered in the presence of positive [14][15][16][17] as well as negative [15,[17][18][19][20][21] values of the cosmological constant Λ. The theories with positive values of Λ (corresponding to the de Sitter (dS) space) are relevant from observational point of view as they describe a more realistic description of the compact stars in the universe since all the observations seem to indicate the existence of a positive cosmological constant.…”

Section: Introductionmentioning

confidence: 99%

Charged compact boson stars and shells in the presence of a cosmological constant

2016

Phys. Rev. D

In this work we study the boson stars and boson shells in a theory involving massive complex scalar fields coupled to the U(1) gauge field and gravity in a conical potential in the presence of a cosmological constant Λ which we treat as a free parameter taking positive and negative values and thereby allowing us to study the theory in the de Sitter and Anti de Sitter spaces respectively. Boson stars are found to come in two types, having either ball-like or shell-like charge density. We have studied the properties of these solutions and have also determined their domains of existence for some specific values of the parameters of the theory. Similar solutions have also been obtained by Kleihaus, Kunz, Laemmerzahl and List in a theory involving massless complex scalar fields coupled to the U(1) gauge field and gravity in a conical potential in the absence of a cosmological constant Λ.

“…We present a detailed discussion of the various regions in our phase diagram with respect to four bifurcation points. Our theory is seen to have rich physics in a particular domain for positive values of Λ which is consistent with the accelerated expansion of the universe.Introduced long ago [1-3], boson stars represent localized self-gravitating solutions studied vary widely in the literature [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Such theories are being considered in the presence of positive [14-16] as well as negative [17][18][19][20] values of the cosmological constant Λ.…”

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confidence: 99%

New results on charged compact boson stars

2016

Phys. Rev. D

In this work we present some new results which we have obtained in a study of the phase diagram of charged compact boson stars in the theory involving massive complex scalar fields coupled to the U(1) gauge field and gravity in a conical potential in the presence of a cosmological constant Λ which we treat as a free parameter taking positive and negative values and thereby allowing us to study the theory in the de Sitter and Anti de Sitter spaces respectively. In our studies, we obtain four bifurcation points (possibility of more bifurcation points being not ruled out) in the de Sitter region. We present a detailed discussion of the various regions in our phase diagram with respect to four bifurcation points. Our theory is seen to have rich physics in a particular domain for positive values of Λ which is consistent with the accelerated expansion of the universe.Introduced long ago [1][2][3], boson stars represent localized self-gravitating solutions studied vary widely in the literature [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Such theories are being considered in the presence of positive [14][15][16] as well as negative [17][18][19][20] values of the cosmological constant Λ. The theories with positive values of Λ (corresponding to the de Sitter (dS) space) are relevant from observational point of view as they describe a more realistic description of the compact stars in the universe since all the observations seem to indicate the existence of a positive cosmological constant. Such theories are also being used to model the dark energy of the universe. However, the theories with negative values of Λ (corresponding to the Anti de Sitter (AdS) space) are meaningful in the context of AdS/CFT correspondence [24][25][26].In fact, cosmological constant, the value of the energy density of the vacuum of space is the simplest form of dark energy and it provides a good fit to many cosmological observations. A positive vacuum energy density resulting from a positive cosmological constant (implying a negative) pressure gives an accelerated expansion of the universe consistent with the observations. Our theory is seen to have rich physics in a particular domain for positive values of Λ.have studied In a recent paper [15], we have studied the boson stars and boson shells in a theory of complex scalar field coupled to U (1) gauge field A µ and the gravity in the presence of a fixed positive cosmological constant Λ (i.e. in the de Sitter space). In the present work we study this theory of complex scalar field coupled to U (1) gauge field A µ and the gravity in the presence of a potential: V (|Φ|) := (m 2 |φ| 2 + λ|φ|) (with m and λ are constant parameters) and a cosmological constant Λ which we treat as a free parameter and which takes positive as well as negative values and thereby allowing us to study the theory in the dS as well as in the AdS space. We investigate * sanjeev.kumar.ka@gmail.com † ushakulsh@gmail.com, ushakuls@iastate.edu ‡ dskulsh@gmail.com, dayakuls@iastate.edu the properties...