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arXiv:1903.04379v1 [gr-qc] 11 Mar 2019 uinke l[1 sue httecsooia con- cosmological the poly- that the assumed Λ [10]. Also al [11] stant et al Setare [9]. by et al formulated Kubiznak been et has Delsate hole black by tropic described been has rsue[,9 3 14], 13, 9, [8, ∗ n rtlwo lc oetemdnmc 8 9] [8, hole black of law first and ihtebakhl hroyaisvlm 8 9] [8, thermodynamics hole black the with unl,teVndrWasbakhl in hole Subse- black [8]. Waals al dar et Van Rajagopal black the by Waals quently, dar determined Van been The has triple [7]. hole and in studied transitions, been Van phase have as points reentrant such fluids, concepts Waals the of from Van terms der holes in the black chemistry, of to concepts of similar The viewpoint qualitatively 6]. behaviour [5, is fluid the hole Walls included, der black are AdS hole the black ro- of order AdS and/or Reissner- the charge first of the charged the tation When non-rotating investigated hole. the black 4] Nordstrom-AdS in [3, transition al phase et After Chamblin hole. that non- black of Schwarzschild-AdS Hawk- properties uncharged thermodynamic con- the correspondence. rotating studied is AdS AdS/CFT [2] al asymptotically to there et ing due of years [1] physics recent hole the In black in interest years. siderable many for studied [email protected] hroyai rpriso lc oehv been have hole black of properties Thermodynamic < hroyai lc oewt oie hpyi Gas Chaplygin Modified with Hole Black Thermodynamic 1] hc ersnstethermodynamic the represents which [12], 0 ASnmes 42.b 45.h 04.70.-s 04.50.Gh, 04.20.Jb, numbers: ca PACS we then and weak tha show the system. a also We as examine this considered by hole. also be black We can of gas fluid Chaplygin system. source of the equations thermodynamic tempe for field and a conditions Einstein’s as of volume, solution gas new hole, lygin a black find w the We thermodynamics of system. hole mass black the (AdS) written Sitter anti-de totically easm httengtv omlgclcntn satherm a as constant cosmological negative the that assume We I. δM INTRODUCTION p V = = = δS T −  8 Λ ∂M π ∂p + = δp V  ninIsiueo niern cec n Technology, and Science Engineering of Institute Indian 8 S,... πl 3 + 2 ..... hbu,Hwa-1 0,India. 103, Howrah-711 Shibpur, d saHa Engine Heat a as -dimensions eateto Mathematics, of Department Dtd ac 2 2019) 12, March (Dated: ja Debnath Ujjal (3) (1) (2) where fsae ow osdrtesai peial symmetric spherically [8–10] static metric the hole consider gas black we So Chaplygin equation above state. with the of construct with hole coincide to drives black thermodynamics want which whose We AdS asymptotically dark Universe. of the an candidate of the acceleration of the one is gas eengtv ersnstevcu rsue The hole black the pressure. of vacuum and the volume represents mass, entropy, Λ negative Here fsaei ie y[15] by given equation the is whose assume hole state we black of AdS hole, in black gas AdS Chaplygin in modified [10] gas polytropic and where, aigi ihtecrepnigfli qaino state, etc. pressure, of volume, equation temperature, fluid the construct corresponding may we the with it paring eaueo h lc oe rmti,a qaino state of equation an this, From p hole. black the of perature o suetengtv omlgclcntn ,s the so are Λ, equations constant Einstein’s cosmological negative the assume function Now unknown the Here where = oiae ytewrsfrVndrWasfli 8 9] [8, fluid Waals der Van for works the by Motivated p ( ∗ ,T V, ,B α B, A, M t oie hpyi a.W have We gas. Chaplygin modified ith II. h hroyai lc oewith hole black thermodynamic the t d lc oewt oie Chap- modified with hole black AdS stemass, the is dnmclpesr n h asymp- the and pressure odynamical a ewitnfrtebakhl n com- and hole black the for written be can ) clt okdn n t efficiency its and done lculate auedet h thermodynamic the to due rature f HPYI LC HOLE BLACK CHAPLYGIN ≡ ds r osat.TemdfidChaplygin modified The constants. are togaddmnn energy dominant and strong , f 2 G ( = ,ρ r, µν − p = ) Λ + fdt S = steetoyand entropy the is 2 g Aρ r l µν 2 2 + g − − dr 8 = ( f ,ρ r, 2 ρ 2 B M r α πT + st edetermined. be to is ) − µν r 2 g d . ( Ω ,ρ r, 2 2 T (6) ) stetem- the is (4) (7) (5) 2

2 are related to the horizon radius rh such that [8–10] F2(r)= −8Bπ(A +2α − Aα)r − 3B(α + 2)Y (r) A S = = πr2 , (8) ′ ′ 4 h −3(A +2α +2Aα)Z(r) − 3BαrY (r) − 3ArZ (r), (18)

4π 1 ′ M = r3 p − r g(r ,ρ) , (9) F3(r)= −3Bα(X(r)+ rX (r)), (19) 3 h 2 h h

2 2 ′ F4(r)= −8B απr +3BαZ(r) − 3BαrZ (r) (20) ∂M 4π 3 1 ∂g(rh,ρ) dp V = = r − rh / , (10) ∂p 3 h 2 ∂ρ dρ From the identity equation (15), comparing the co- efficients of powers of ρ in both sides, we must get Fi(r)=0, i = 0, 1, 2, 3, 4. Now set F (r)=0= F (r), 1 ∂f(r, ρ) 0 3 T = we get (from equations (16) and (19)) 4π ∂r  r=rh X X(r)= 0 (21) r g(rh,ρ) 1 ∂g(r, ρ) =2rhp − − (11) where X0 is an integration constant. Next put F1(r)=0 4πrh 4π ∂r r rh   = in equation (17), we have Now assume that all the thermodynamic parameters for 8π 2 2 1+ A black hole related with the parameters for modified Chap- Y (r)= Ar − Y0r (22) lygin gas. So the first law of thermodynamics yields (us- 3 ing integrability condition) [10] where Y0 is an integration constant. Again put F4(r)=0 ρ + p in equation (20), we must get S = V (12) T 8π 2 Z(r)= − Br − Z0r (23) Using equations (4) and (8)-(11), the equation (12) re- 3 duces to where Z0 is another integration constant. Lastly, we set − ∂g(r, ρ) F3(r) = 0, we obtain (from equation (18)) the relation 24πr2(Aρ − Bρ α) − 3g(r, ρ) − 3r ∂r between two parameters as   α A = − (24) − − (1 + A)ρ − Bρ α × 1+ α For non-trivial solutions of X,Y,Z, we must have α 6=   0, A 6=0,B 6= 0. Putting the solutions of X(r), Y (r) and ∂g(r, ρ) − − −1 × 16πr2 − 6 A + αBρ 1 α = 0 (13) Z(r) in equation (14), we get the expression of g(r, ρ) as ∂ρ   in the following form:  Since g(r, ρ) is unknown function of r and ρ, so without X0 8π 2 g(r, ρ)= + Ar2 − Y r1+ A ρ any loss of generality, we may assume the polynomial r 3 0 form of g(r, ρ) as in the following form  

− g(r, ρ)= X(r)+ Y (r)ρ + Z(r)ρ α (14) 8π − + − Br2 − Z r ρ α (25) 3 0 where X(r), Y (r) and Z(r) are arbitrary functions of   r. Now substituting the expression of g(r, ρ) in equation Finally, putting the expression of g(r, ρ) in equation (6), (13), we obtain the following equation we obtain the solution of the function f(r, ρ): −α −α−1 F0(r)+ F1(r)ρ + F2(r)ρ + F3(r)ρ 2M + X0 2 − f(r, ρ)= − + Y r1+ A ρ + Z rρ α (26) r 0 0 − − + F (r)ρ 2α 1 = 0 (15) 4 This is a new form of black hole solution which may be Chaplygin black hole where called (after the names of Van der Waals black hole [8] and polytropic black hole [10]). Since ′ 3 2 the thermodynamic pressure p = 2 depends on l and F0(r)= −3A(X(r)+ rX (r)), (16) 8πl compare this pressure with the fluid pressure (eq.(4)), we may obtain the expression of density ρ, which also 2 ′ 2 F1(r)=8A(A − 2)πr + 3(A + 2)Y (r) − 3ArY (r), (17) depends on l and ρ can be written in terms of pressure p 3 explicitly for some suitable values of α. So from equation III. CLASSICAL (27), we have

2 In thermodynamics and engineering, a heat engine 2M + X0 1+ A Aρ − p f = − + Y0r ρ + Z0r (27) is a system that converts heat or thermal energy and r B chemical energy to mechanical energy, which can then be where ρ can be calculated from Aρα+1 − pρα − B = 0 used to do mechanical work. That means a heat engine is 3 with p = 8πl2 . So from equation (27), we may say that a physical system that takes heat from hot reservoir and the black hole solution depends of r and thermodynamic part of it converts into the works while the remaining pressure p (which is obviously a constant). In particular, is transferred to cold reservoir. In 2014, Johnson [16] 8πp if we choose α = −2/3, X0 = Z0 = 0 and Y0 = ρ , then has introduce the holographic heat engine for black from equations (25) and (27), we obtain hole, where the cosmological constant was considered a thermodynamic variable. Based on the holographic r2 2M f = − (28) heat engine for black hole proposal, Johnson [17–19] l2 r has studied the Gauss-Bonnet black holes, Born-Infeld which is a black hole solution with asymptotically AdS AdS black holes and holographic heat beyond spacetime. large N and the exact efficiency formula. Heat engines for dilatonic Born-Infeld black holes have been analyzed Now we examine the weak, strong and dominant energy in [20]. Zhang et al [21] have studied the f(R) black conditions for the source fluid. The energy momentum holes as heat engines. The thermodynamic efficiency tensor for the anisotropic source fluid is given by [8–10] in charge rotating and dyonic black holes has been studied in [22]. Till now, several authors have studied 3 the heat engine mechanism for various types of black µν µ ν µ ν T = ̺e0 e0 + piei ei (29) holes [23–37, 39–44, 47]. Recently Setare et al [45] i=1 X have discussed polytropic black hole as a heat engine. Motivated by their work, here we’ll study the classical where ̺ is the energy density, pi (i = 1, 2, 3) are the µ heat engine for our Chaplygin black hole. for the source fluid and ei are the components of the vielbein. Now for the black hole metric (5), using The horizon radius rh can be found from the equation the Einstein’s equation (7), we obtain the field equations 2 2+ A 2 −α [8–10] (assume that the gravitational constant G = 1) Y0rh ρ + Z0rhρ − X0 − 2M = 0, which depends on X0, Y0,Z0,α,ρ. From equations (8) and (10), we obtain 1 − f − rf ′ ̺ = −p = + p the volume 1 8πr2

1 S 1+ A αZ0 −α−1 1 2 2 3 1+ A −α Y0 π − π ρ S = 1+ Y0r ρ − 2Z0rρ + (30) V = (32) 8πr2 α 8πl2 2(A + Bαρ−α−1)    and Also from equation (11), we get the temperature rf ′′ +2f ′ p = p = − p 1 2M + X0 Z0(Aρ − p) 2 3 16πr T = 1+ − (33) A 2S 2πAB   1 1 2 2 −α 3 which can be written as = 1+ Y r1+ A ρ + Z rρ − (31) 8πr2 α α 0 0 8πl2     π(1 + A)(2M + X0) S = −α−1 (34) Now it is easy to check that the weak energy condition: 2πAT + Z0ρ ̺ ≥ 0, ̺ + pi ≥ 0 (i = 1, 2, 3) may be satisfied for Y0 ≥ So the relation between V and T is obtained as in the 0, Z0 ≤ 0 and α > 0. The strong energy condition: form ̺ + i pi ≥ 0, ̺ + pi ≥ 0 may be satisfied for Y0 ≥ 0, 1 Z0 = 0 and α ≥ −2/3. The dominant energy condition: 1+ A −α−1 (1+A)(2M+X0 ) αZ0(1+A)(2M+X0)ρ P Y −α−1 − −α−1 ̺ ≥ |pi|, (i =1, 2, 3) may be satisfied for Y0 ≥ 0, Z0 ≤ 0 0 2πAT −Z0ρ 2πAT −Z0ρ V = and 0 < α ≤ 2. So all the energy conditions will be  2(A + Bαρ−α−1) satisfied at a time if Y0 ≥ 0, Z0 = 0 and α> 0. In other (35) cases, the above energy conditions may be violated. If we To describe the thermodynamic behavior of the Chap- assume the above conditions of the parameters, we may lygin gas in presence of variable pressure (i.e., variable checked that the energy conditions are satisfied on the cosmological constant), one can identify mass M from horizon. For Van der Waals black hole [8, 9], some of the being the energy U to being the [46], i.e., the energy conditions are violated but for polytropic black enthalpy function is defined by H = M = U + pV . From hole [10], all the energy conditions are satisfied. In our the first law of thermodynamics, we get Chaplygin black hole, some of the energy conditions are satisfied for some restrictions of the parameters involved. dH = dM = T dS + V dp (36) 4

By integration the above equation, the enthalpy function where ρi can be calculated from the relation pi = Aρi − −α can be written in the form: Bρi , i = 1, 2, 3, 4. The p-V diagram [16] shows the 1 Carnot heat engine which forms a closed path in figure 2. 1 Y ρ S 1+ A Z S H = − X + 0 + 0 (37) The work done by the heat engine is 2 0 2 π 2πρα   W = QH − QC (47) The Gibb’s free energy is given by [47]

1 The efficiency of a heat engine relates how much useful 1+ A 1 Y0ρ S work is output for a given amount of heat energy input G = H − TS = − X0 − (38) 2 2A π and it is defined by   Also the free energy is given by [47] W Q η = =1 − C (48) 1 QH QH 1 Y ρ S 1+ A F = G − pV = − X − 0 2 0 2A π We know that the has the maximum effi-   1 ciency. Also we mention that the consists S 1+ A αZ0 −α−1 pY0 π − π ρ pS of two isothermal processes plus two isochores processes. − −α−1 (39) 2(A + Bαρ ) So the maximally efficient Carnot engine is also a . For Carnot cycle, V1 = V4 and V2 = V3, so we David Kubiznak and Robert B. Mann [48] have showed have the maximum efficiency as the critical behaviour of charged AdS black holes. Follow- ing this, we will study the critical behavior of the Chap- T η =1 − C (49) lygin black hole. Critical point is a point of inflection max T which can be found from the following conditions: H which is the maximum one of all the possible cycles be- ∂p ∂2p tween the given higher temperature T and lower one =0, 2 = 0 (40) H ∂rh ∂r  cr  h cr TC. The specific heat of the thermodynamical system is At the critical point r , the critical pressure p and cr cr ∂S 2AS2T critical temperature Tcr will be C = T = − × ∂T (1 + A)(2M + X0) − 1 α   α+1 2 α+1 −α−1 Y0 α Y0 −2 Z0αρ ∂p pcr = A rcr − B r (41) 1 − (50) αZ αZ cr 2πA(A + Bαρ−α−1) ∂T  0   0    and If volume V is constant (i.e., S is constant), the we can α α+1 obtain 2M + X Z Y − T = 0 + 0 0 r 2 (42) cr 2πα 2πA αZ cr −α−1 "  0  # ∂p 2πA(A + Bαρ ) = −α−1 (51) ∂T Z0αρ with the condition  V − 1 α+1 and hence consequently for constant volume, the specific Y0(α + 1) Y0 ∂p 2M + X0 = (43) heat C = 0. For constant pressure, = 0, so we α αZ V ∂T  0  p may obtain the specific heat for constant pressure as Now assume, TH and TC are the of the hot and cold reservoirs respectively and they consist of 2AS2T two isothermal processes with two adiabatic processes. Cp = − (52) (1 + A)(2M + X ) The heat engine flow is shown figure 1 [16]. So the heat 0 flow for the upper isotherm process from 1 to 2 is given which is not equal to zero. So we have a new engine, by [16] described in figure 3, which involves two isobars and two isochores/adiabats [16]. The heat flows show along the Q = T △S → = T (S − S ) (44) H H 1 2 H 2 1 top and bottom. The work done along the isobars is given and the exhausted heat from the lower by is given by [16] W = △p4→1 △V1→2 = (p1 − p4)(V2 − V1) QC = TC△S3→4 = TC (S3 − S4) (45) 1 1 S2 1+ A S1 1+ A Y0 π π = (p1 − p4) − − − − − Here Si’s are related to Vi’s satisfying  2 (A + Bαρ α 1) (A + Bαρ α 1)   2  1  1+ 1 − − Si A αZ0 α 1  −α−1 −α−1 Y0 π − π ρi Si αZ0 ρ2 S2 ρ1 S1 Vi = − − , i =1, 2, 3, 4. (46) −  − − − − − (53) 2(A + Bαρ α 1) 2π (A + Bαρ α 1) (A + Bαρ α 1)  i  2 1  5

The net inflow of heat in upper isobar is given by Chaplygin black hole solution may be reduced to the polytropic black hole solution for negative Λ. If we set T2 1 A = 2, Y0 = l2ρ and Z0 = 0, the Chaplyin black hole QH = Cp(p1,T )dT (54) T1 may be reduced to the asymptotically AdS black hole Z 1 for negative Λ. Also if we set A = −2, Y0 = ρ and which can be expressed as X0 = Z0 = 0, the Chaplyin black hole may be reduced to the Schwarszchild black hole. We have also examined (A + 1)(2M + X ) Q = 0 the weak, strong and dominant energy conditions for the H 2A source fluid of the Chaplygin black hole. For Y0 ≥ 0, 4πAZ ρ−α(T − T ) 0 2 1 Z0 ≤ 0 and α> 0, the weak energy condition is satisfied, × −α −α (2πAT1 + Z0ρ1 )(2πAT2 + Z0ρ1 ) for Y0 ≥ 0, Z0 ≤ 0 and α ≤ −2/3, the dominant  − α energy condition is satisfied and for Y0 ≥ 0, Z0 = 0 2πAT1 + Z0ρ1 +Log − (55) and 0 < α ≤ 2, the strong energy condition is satisfied 2πAT + Z ρ α  2 0 1  but for other cases, the all energy conditions are violated. or in the other form: We have described the classical heat engine for Chap- −α (1 + A)(2M + X0) S2 Z0ρ1 lygin black hole. Using the horizon radius rh, we have QH = Log + (S1 − S2) 2A S1 2πA found the relations between volume V , temperature T , (56) entropy S and pressure p (or density ρ). Using the first Finally we can demonstrate the performance of the heat law of thermodynamics, we have found the enthalpy engine by a thermal efficiency η and found in the following function in terms of the entropy S. The Gibb’s free form: energy and free energy have been evaluated. The critical pressure and critical temperature have been found at W p η = = 1 − 4 × the critical point of the system. We have found the heat Q p H  1  flows from upper and lower isotherms process. Also we 1 1 S2 1+ A S1 1+ A have calculated the work done by the heat engine and Y0p1 π π its efficiency. We have found the maximum efficiency by −α−1 − −α−1  2 (A + Bαρ ) (A + Bαρ ) the Carnot cycle. For static black holes, Johnson [16]   2  1   −α−1 −α−1 has investigated that the Carnot and Stirling cycles are αZ0p1 ρ2 S2 ρ1 S1 coincided. For constant volume, we found that specific −  − − − − − × 2π (A + Bαρ α 1) (A + Bαρ α 1)  2 1  heat CV = 0. On the other hand, for constant pressure, we have found that specific heat Cp 6= 0. So we have considered another cycle which consists of two isobars −α −1 (1 + A)(2M + X0) S2 Z0ρ and two isochores. We have calculated the net inflow of Log + 1 (S − S ) 2A S 2πA 1 2 heat in upper isobar and efficiency of the heat engine for  1  (57) this cycle. which crucially depends on the modified Chaplygin gas parameters α, A and B.

IV. DISCUSSIONS

We have assumed the negative cosmological constant as a thermodynamical pressure and the asymptotically anti-de Sitter (AdS) black hole thermodynamic param- eters which are identical with the modified Chaplygin gas, which obeys the integrability condition of the thermodynamical system. We have written the mass of the black hole, volume, entropy and temperature due to the . We found the solutions of Einstein’s field equations of AdS black hole for modified Chaplygin gas. The new form of solution for black hole may be called Chaplygin black FIG. 1: The figure represents the heat engine flows [16]. hole (after the names of Van der Waals black hole [8] and polytropic black hole [10]). For A = 0, the above

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